Sex Determination

SEX DETERMINATION

The problem of sex determination has been one of the most important biological puzzle up to the year 1900.

A number of theories were postulated from time to time by the biologists to explain this critical phenomenon.

Hippocrates and other theorists believed that the age or vigour of the parents was responsible for determining the sex of the offspring. The older or more vigorous parent tries to impress its sex upon the offspring.

According to some philosophers if an egg is fertilized soon after ovulation it gives rise to female but if it remains in the oviduct for sometime before fertilization it produces male. Galen and various others claim that germ cells from the right ovary produce males while the germ cells from the left ovary produce females.

Professor Shenk of Vienna put forward the Nutrition Theory. He assumed that high degree of nourishment to the mother brings about female offspring while less nutrition causes male offspring’s. These speculations of the early biologists are now replaced by more genetic and scientific theories.

Modern Theories of Sex Determination:

The Modern Theories Given For Sex Determination Are As Follows:

(1)Chromosomal theory or Theory of Heterogamy

(2) Genic balance theory

(3) Hormonal theory

(4) Theory of environmental factors.

(1)Chromosomal Theory or Theory of Heterogamy:

The complete account of chromosomal sex determination was at first worked out by Stevens (1905). This view was later supported by other scientists such as Wilson, Bridge, Goldschmidt and Whitings.

In majority of sexually reproducing animals two types of chromosomes are found:

(i) Autosomes:

They are found in all cells. The genes present on autosomes are responsible for determining the somatic characters but sometime influence the sex of the organism. The two members of each homologous pair are similar in shape and size (homomorphic).

(ii) Sex Chromosomes or Allosomes:

They carry genes for sex. A pair of them determines the sex. They are variously named as X and V chromosomes (Man and Drosophila), Z and W chromosomes (Birds and Moth),oddchromosomes,idiosoines,heterosomes or allosomes.

The genes which determine the sex are being located on these chromosomes.The two members of this pair arc often dissimilar in male and are represented as X and Y chromosomes or as Z and W chromosomes.

(a) XX Female and XY Male Types:

This type of sex mechanism is found in Drosophila (fruitfly) and majority of mammals including man. In this type the female is homogametic (XX) and male 

is heterogametic (XY) consisting of two dissimilar chromosomes X and Y. The females produce ova all of one type having X chromosome. Males produce two types of sperms: -50% with X-chromosome and remaining 50% with Y-chromosome. Thus, the sex chromosomes in female are homomorphic and those of male are heteromorphic (Fig. 5.13).

(b) ZW Female and ZZ Male Type:

In butterflies and birds, the female is heterogametic having dissimilar Z and W chromosomes whereas the male is homogametic having similar ZZ chromosomes (It is a convention to designate female as ZW instead of XY and male as ZZ instead of XX). The situation here is just reverse to first type.

(c) XX Female and XO Male Type:

Mc Clung and Wilson (1903) described this type of sex mechanism in insects especially in grasshopper. In male there is no mate for X chromosome, hence the name XO is given, there is no Y chromosome. They produce sperm of two types, 50% with X chromosome and 50% without X. In females there are two similar or homomorphic sex chromosomes XX.

2. Genic Balance Theory:

This theory was proposed by Calvin Bridges (1921). From his study on Drosophila he suggested that the X chromosomes carry factor for femaleness whereas autosomes “A” carry genes for maleness. Y chromosome does not take part in sex determination. From the Fig. 5.15 it is clear that the genic balance is governed by the ratio of the number of X-chromosomes to the number of sets of autosomes in the zygote at fertilization.

II the ratio is 1.0 the offspring develops into female, but if it is 0.5, then the offspring develops into male. If the ratio is intermediate between 1.0 and 0.5,the resulting individual is neither a male or nor a female but an inter sex. Super females have a ratio of 1.5 and super males have a ratio 0.33.

(3.) Hormonal Theory:

Hormones are the secretion of the endocrine glands which in many instances modify the sex rather determining the sex. They are mainly responsible for the expression of secondary sexual characters. This theory is based upon the observation of Crew in chicks.

In course of his investigation he found a hen which laid fertile eggs, accidentally lost its ovary, stopped laying eggs, and developed male characters such as comb and male plumageand became a cock. The above case of sex reversal is explained by assuming that destruction or removal of the ovary led to stoppage of production of the ovarian hormones.

But the rudiment of testis (present in all female birds) became functional following the loss of ovary and produced male hormone which is responsible for the appearance of male secondary sexual characters. Such a male produced sperms and became father of two chickens.

Another classical example of sex reversal by the action of hormone is observed in free martin. In cattle, when twin calves of opposite sex are born, the female is usually somewhat abnormal and sterile. Such a calf is called freemartin.

Since the male hormone appears earlier in the development, it passes into the body of the under developed female through the circulation and causes partial sex reversal of the female.

(4) Theory of Environmental Factors:

Baltzer (1935) observed sex determination due to external environment in certain lower animals such as Bonellia. The adult female is several inches long but the male is very small of the size of large protozoa and lives in the reproductive tract of the female. The newly hatched young worm (Bonellia), when reared in isolation, develops into a female. But when, these are released into water containing mature females, some of them attach to the proboscis of female (to suck nourishment) develop into tiny males and come to lie in the oviduct of the female.

Sex determination in humans:

In human beings, sex is determined by genetic inheritance. Genes inherited from the parents determine whether an offspring will be a boy or a girl.

Genes for all the characters are linearly arranged on chromosomes. These include the genes for sexual characters.

Generally, characters related to the reproductive system are called sexual characters and those that are not are called vegetative characters.

The chromosomes that carry genes for sexual characters are called sex chromosomes, while those that carry genes for the vegetative characters are called autonomies.

A sex chromosome that carries the genes for male characters is called Y chromosome and one which carries the genes for female characters is called X chromosome.

We have a total of 46 chromosomes. Half of them come from the mother and the rest, from the father. Out of these 46 chromosomes, 44 are autonomies and 2 are sex chromosomes. The sex chromosomes are not always a perfect 

pair.

In females there are 44 autonomies and two X chromosomes, in males there are 44 autonomies, one X chromosome and one Y chromosome. So the chromosomes in woman are 44 + XX, while the chromosomes in man are 44 + XY. 

Let us see the inheritance pattern of X and Y chromosomes.

During gamete formation, the normal diploid chromosome number is halved. This is called the haploid condition. All the eggs of a female have 22 + X chromosomes. A male produces two types of sperms—one type bears the 22 + X composition and the other, 22 + Y. Therefore, in every 100 sperms, 50 have Y chromosomes and 50 have X chromosomes.

Any one of the two types of sperms can fertilize the egg. If a Y-bearing sperm fertilizes the egg, the zygote has the 44 + XY composition, and the resulting embryo grows to be a boy. When an X-bearing sperm fertilizes the egg, the resulting zygote has the 44 + XX composition. This embryo develops into a girl.

All the children inherit one X chromosome from the mother.Therefore, sex is always determined by the other sex chromosome that they inherit from the father. One who inherits the X chromosome of the father is a girl, while one who inherits the Y chromosome of the father is a boy.

DIFFUSION

DIFFUSION:

DEFINITION:

“The tendency on the part of molecules, atoms, ions, etc., of gases, liquids and solids to get evenly distributed throughout the available space on account of their ran­dom kinetic motion is called diffusion.”

Random kinetic motion of particles is due to kinetic energy present in them.

Diffusion is also defined as the movement of the particles of different substances from the region of their higher concentration, free energy or diffusion pressure to region of their low concentration, free energy or diffusion pressure.

Diffusion is dependent upon the number of particles per unit volume, density of medium, distance through which diffusion is to occur, temperature and pressure.

Diffusion will be more rapid when the difference in concentration is larger. Gases diffuse more rapidly than liquids. Solids are the slowest to diffuse. When the particles of diffusing substance get evenly distributed, a state of equilibrium is reached. It stops further movement.

Diffusion of particles of one substance is independent of the diffusion of particles of another substance, provided the two do not react. It is known as independent diffusion. The diffusion pressure of the individual substance is then known as partial pressure.

Thus in photosynthesizing leaf, water vapours and oxygen diffuse out while carbon dioxide enters the leaf depending upon the differences in their partial pressures in the leaf interior and the outside. Diffusion is also responsible for uptake and distribution of water and solutes.

(i) Open a bottle of perfume in one comer of room. Soon odour of the perfume will be felt throughout the room,

(ii) Place a crystal of copper sulphate in a beaker containing water.

An intense blue colour will be seen around the crystal. It decreases with the increase of distance from the crystal. It shows that copper sulphate molecules are diffusing into water (Fig. 11.3). Water molecules will also move towards copper sulphate crystal in order to occupy that space. Ultimately the molecules of the two, water and copper sulphate, will be evenly distributed throughout the solution.

Diffusion Pressure (D.P.):

The pressure exerted by the tendency of the particles to diffuse from the area of its higher concentration to the region of its lower concentration is called diffusion pressure. It is proportional to the concentration of diffusing particles. A porous pot is fitted to a glass tube, one end of which dips in water.

A gas jar filled with hydrogen is inverted over the porous pot. Hydrogen has the ability to diffuse more rapidly into porous pot than the ability of air to diffuse out of the porous pot. This develops a pressure inside the porous pot which pushes the air from the tip of glass tube into water in the form of air bubbles (Fig. 11.4).

Factors Influencing Diffusion:

(i) Density:

Rate of diffu­sion of a substance is inversely proportional to square root of its relative density (Graham’s Law).

(ii) Permeability of Medium:

Rate of diffusion decreases with density of the medium.

(iii) Temperature:

A rise in temperature increases the rate of diffusion with Q10 = 1-2-1-3. Because of it sugar crystals do not dissolve easily in ice cold water while they do so easily in warm water.

(iv) Diffusion Pressure Gradient:

Rate of diffusion is directly proportional to the difference of diffusion pressure at the two ends of a system and inversely proportional to the distance between the two.

Importance of Diffusion in Plants:

(i) Diffusion keeps the cell walls of the internal plant tissues moist.

(ii) It is a means of spreading of ions and other substances throughout the protoplast.

(iii) Tran­spiration or loss of water in vapour forms is a diffusion process.

(iv) Exchange of gases (CO2 and O2) between the plant interior and outside air occurs through diffusion.

(v) Osmosis is a special type of diffusion in which water diffuses through a semi-permeable membrane.

(vi) Aroma of flowers is due to diffusion of volatile aromatic compounds to attract pollinating animals.

Significance of Diffusion:

1. The process of diffusion is involved in the transpiration of water vapours.

2. Gaseous exchange during the process of respiration and photosynthesis takes place with the help of diffusion.

3. During passive salt uptake the ions are absorbed by the process of diffusion.

4. It also helps in translocation of food materials.

5. Gas exchange in submerged hydrophytes takes place by general body surface (epidermis) through diffusion.

6. Aroma of flowers is due to diffusion of volatile aromatic compounds to attract insects.

WATER POTENTIAL

WATER POTENTIAL:

DEFINITION:

“The measure of the relative tendency of water to move from one area to another is called water potential, and is commonly represented by the Greek letter Ψ (Psi).”

Water potential term was coined by Slatyer and Taylor (1960). It is modern term which is used in place of DPD. The movement of water in plants cannot be accurately explained in terms of difference in concentration or in other linear expression.

The best way to express spontaneous movement of water from one region to another is in terms of the difference of free energy of water between two regions (from higher free energy level to lower free energy level).

According to principles of thermodynamics, every components of system is having definite amount of free energy which is measure of potential work which the system can do. Water Potential is the difference in the free energy or chemical potential per unit molar volume of water in system and that of pure water at the same temperature and pressure.

It is represented by Greek letter or the value of is measured in bars, pascals or atmospheres. Water always moves from the area of high water potential to the area of low water potential. Water potential of pure water at normal temperature and pressure is zero. This value is considered to be the highest. The presence of solid particles reduces the free energy of water and decreases the water potential. Therefore, water potential of a solution is always less than zero or it has negative value.

Components of Water Potential:

A typical plant cell consists of a cell wall, a vacuole filled with an aqueous solution and a layer of cytoplasm between vacuole and cell wall. When such a cell is subjected to the movement of water then many factors begin to operate which ultimately determine the water potential of cell sap.

For solution such as contents of cells, water potential is determined by 3 major sets of internal factors:

(a) Matrix potential (Ψm)

(b) Solute potential or osmotic potential (Ψs)

(c) Pressure potential (Ψp)

(a) Matrix potential (Ψm):

Water potential in a plant cell or tissue can be written as the sum of matrix potential (due to binding of water to cell and cytoplasm) the solute potential (due to concentration of dissolve solutes which by its effect on the entropy components reduces the water potential) and pressure potential (due to hydrostatic pressure, which by its effect on energy components increases the water potential).

Ψw = Ψs + Ψp + Ψm

In case of plant cell, m is usually disregarded and it is not significant in osmosis. Hence, the above given equation is written as follows.

Ψw = Ψs + Ψp

(b) Solute potential or osmotic potential (Ψs):

It is defined as the amount by which the water potential is reduced as the result of the presence of the solute, s are always in negative values and it is expressed in bars with a negative sign.

(c) Pressure potential (Ψp):

Plant cell wall is elastic and it exerts a pressure on the cellular contents. As a result the inward wall pressure, hydrostatic pressure is developed in the vacuole it is termed as turgor pressure. The pressure potential is usually positive and operates in plant cells as wall pressure and turgor pressure. Its magnitude varies between +5 bars (during day) and +15 bars (during night).

Important Aspects of Water Potential (Ψw):

(1) Pure water has the maximum water potential which by definition is zero.

(2) Water always moves from a region of higher Ψw to one of lower Ψw.

(3) All solutions have lower w than pure water.

(4) Osmosis in terms of water potential occurs as a movement of water molecules from the region of higher water potential to a region of lower water potential through a semi permeable membrane.

Osmotic Relations of Cells According to Water Potential:

In case of fully turgid cell:

The net movement of water into the cell is stopped. The cell is in equilibrium with the water outside. Consequently the water potential in this case becomes zero. Water potential is equal to osmotic potential + pressure potential.

In case of flaccid cell:

The turgor becomes zero. A cell at zero turgor has an osmotic potential equal to its water potential.

In case of plasmolysed cell:

When the vacuolated parenchymatous cells are placed in solutions of sufficient strength, the protoplast decreases in volume to such an extent that they shrink away from the cell wall and the cells are plasmolysed. Such cells are negative value of pressure potential (negative turgor pressure).

Numerical Problems:

1. Suppose there are two cells A and B, cell A has osmotic potential = -16 bars, pressure potential = 6 bars and cell B as osmotic potential = – 10 bars and pressure potential = 2 bars. What is the direction of movement of water?

Water potential of cell A = Ψs +Ψp = – 16 + 6 = – 10 bars

Ψ of cell B = -10 + 2 = -8 bars.

As movement of water is from higher water potential (lower DPD) to lower water potential (higher DPD), hence the movement of water is from cell B to cell A.

2. If osmotic potential of a cell is – 14 bars and its pressure potential is 7 bars. What would be its water potential?

We know Ψw = Ψs + Ψp

Given, osmotic potential (Ψs) is – 14 bars.

Pressure potentials (Ψp) is 7 bars

Therefore,

Water potential = (-14) + 5 = – 9 bars.

Movement of Water from Cell to Cell:

Differences in water potential (∆Ψ) are important for the water movement in and out of the cell. These differences are relevant as compared with the environments. Likewise water moves from cell to cell by diffusing down the water potential gradient between the two cells.

The direction of water movement and the force of movement are linked with water potential in each cell and also on the difference between the water potential of the two cells (Fig. 6-5).

In the instance mentioned below we observe that:

Obviously water will flow from cell B to cell A i.e., towards the lower or more negative water potential.

The value of ∆Ψ is very vital since it is directly proportional to the rate of movement of water from one cell to another.

The rate and amount of water movement is dependent upon the difference in water potential on either side of the membranes.

MECHANISM OF TRANSMISSION OF NERVE IMPULSES

Mechanism of Transmission of Nerve Impulse (explained with diagram):

All the nerve fibres carry information in the form of nerve impulse.

Nerve impulse is the sum total of physical and chemical disturbances created by a stimulus (electrical, chemical or mechanical) in a neuron or nerve fibre which result in the movement of a wave along the nerve fibre.

The nerve fibre or axon is like a cylinder, the interior of which is filled with axoplasm (i.e., the cytoplasm of the nerve cell) and the exterior of which is covered with a thin membrane, the axon membrane or axolemma.

The axon is immersed in the extracellular fluid (ECF). Through axolemma movement of solute takes place between the axoplasm and ECF. Generally the solutes in ECF and axoplasm are in ionic form. In the axoplasm -vely charged protein molecules are present which are neutralized due to the presence of large amount of K+ ions. In the ECF (outside the axon) the -vely charged CI– ions are neutralized by the presence of +vely charged Na+ ions.

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Conduction of nerve impulse is an electro-chemical process. Membrane of a non-conducting nerve cell or neuron is positive on the outside and negative inside. The difference in charge is about 70 to 90 millivolts which is called as resting potential and the membrane is said to be polarized. To maintain resting potential, sodium potassium metabolic pump operates.

This pump which is located on the axon membrane pump Na+ from axoplasm to ECF and K+ from ECF to axoplasm. It pumps more positive charges (3 Na+) from axoplasm to ECF than in the reverse direction (2K+), and is run by an enzyme called Sodium Potassium-ATPase. The concentration of sodium ions will be about 14 times more in ECF (outside) and concentration of potassium ions will be about 28-30 times more in axoplasm (inside).

When a stimulus (may be mechanical, electrical or chemical) is applied to the membrane of the nerve fibre, its permeability changes and sodium potassium pump stop operating. Sodium ions rush inside and potassium ions rush outside. This results in the positive charge inside and negative charge outside.

The nerve fibre is said to be in action potential or depolarized. The resting potential inside the membrane is about -70 mV and the action potential inside the membrane is about +30 mV. The travelling of action potential along the membrane is a nerve impulse. After a period of action potential, again sodium pump operates and axon membrane will get resting potential by repolarization.

During this process the sodium ions will rush outside and potassium ions will move inside (reversal of the process taken place during action potential). Refractory period is the period of complete inexcitibility (restoration of nerve fibre) between deplorization and repolarization (1-6 milli seconds in mammals). During refractory period nerve fibre never transmits impulse.

In medullated nerve fibres (white fibres), the impulse jumps from node to node, it is called saltatory propagation (Fig. 1.21). It increases the speed of nerve impulse which is about 20 times faster in medulated than in non-medullated nerve fibres. The speed of transmission of nerve impulse also depends upon the diameter of the fibre. Fibres with larger diameter conduct impulse faster.

The velocity of conduction of nerve impulse in frog is 30 metres per second and that of mammal is 120 metres per second. The threshold value of any nerve fibre is the minimum strength of stimulus which initiates action potential in that nerve fibre.

ECONOMIC BOTANY

                                     UNIT-(II)

                            Economic  Botany

Cereals:  rice,  wheat and  maize:

1.RICE (Hindi – Chaval or Dbari):

Botanical Name:   Oryza sativa L.

Family:   Gramineae or Poaceae

ECONOMIC USES:

1. Rice is the chief cereal used as staple food in most of the parts of the world.

2. Its fruit is a caryopsis.

3. It is an annual grass which grows luxuriantly in deep waters.

4. The inflorescence is a long panicle with ovate or oblong spikelets.

5. Caryopsis is oblong and angular. It remains tightly enclosed in lemma and palea.

6. Grains contain a large amount of starch, fat and proteins.

7. It is also used in the preparation of many alcoholic beverages.

8. Hats are prepared from the fibres obtained from its stem.

9. Paper, mats and boards are also prepared from rice.

10. Rice-bran oil is used for soaps, cosmetics and also as an anticorrosion oil.

11. Rice husk is used for making activated carbon, sodium silicate and silicon, and also as fuel, packing material and animal feed.

12. West Bengal, Bihar and U.P. are the chief rice- producing Indian states.

2. WHEAT (Hindi – Gehun):

Botanical Name:   Triticum aestivum L. emend. Thall.

Family:   Gramineae or Poaceae

ECONOMIC USES:

1. It is a cereal crop of family Gramineae.

2. It is the most common food plant.

3. The plant attains a height of 2-5 feet.

4. The inflorescence is a spike of spikelets. The spikelets are borne of a zigzag axis.

5. The fruit is a caryopsis.

6. Each grain consists of an outer husk, the aleurone layer containing protein, the endosperm having starch, and the embryo.

7. Wheat flour is used for making bread, biscuits, cakes, pastry and other similar articles. Wheat is also used in the manufacture of beer and other alcoholic beverages.

8. Fruit contains a single endospermic seed which contains many minerals, including Mg, Mn, Cu, Fe and Zn.

9. Wheat straw is used as a fodder for catties and for seating the chairs, mattings, hats, etc.

10. Wheat straw pulp is used for preparing writing-, printing- and wrapping paper, and straw board.

11. In India, wheat is grown mainly in Punjab, U.P., Haryana, Madhya Pradesh, Maharashtra, Rajasthan and Bihar.

12. Important wheat-producing countries are U.S.A., Russia, Australia, China, India, etc.

3.MAIZE (Hindi – Makai):

Botanical Name:  Zea mays L.

Family:   Gramineae or Poaceae.

ECONOMIC USES:

1. It is an annual cereal, attaining a height of 3 to 15 feet.

2. It is the largest amongst the cereals.

3. The stem is jointed, the leaves are large and the aerial prop roots are present in addition to the well-developed fibrous root, system.

4. Flowers are of two types, i.e., terminal tassel bearing the male flowers and cob or ear bearing the female or pistillate flowers (Fig. 71).

5. Styles are long and silky.

6. Cob is covered by large number of leafy bracts.

7. The fruit is a caryopsis consisting of hull (6%), protein or aleurone layer (8 to 14%), endosperm (70%) and embryo (11%).

8. Grains are used by man as well as animals for food.

9. Corn flakes, com starch, com syrup, com oil, dextrins and industrial alcohols are some of the maize products.

pulses:  Bengal  gram,  green  gram,  black  gram:

1.BENGAL GRAM (Chick Pea):

Botanical Name          :           Cicer arientinum

Family                      :           Leguminoceae

Bengal Gram is the most important rabi pulse crop grown in India. Rank first in area as well as in production of gram.

ECONOMIC USES:

1. Tender leaves of young gram crops are used as vegetable.

2. The grain is eaten in raw or boiled as vegetable.

3. The grain is parched and eaten as futanas.

4. Dal is grounded in flour and used in preparation of Besan or Zunka, Shev, Chakli, Bhaji etc.  

5. It is also used for preparation of sweet meats like pura-poli, laddu,mysorepak, bundi, jilebi etc.

6. The malic acid (Amb) is collected from plants which have medicinal value against stomach ache.

7. The broken grains are largely fed to horse and the dried leaves and stalks are used as fodder for cattle.

8. It is a good source of protein and content 16-19% protein.

9. Germinated seeds are good source of vie-E.

2.BLACK GRAM (Urad Dal):

Botanical Name:   Vigna mungo(Linn.) Hepper.

Family:   Leguminoseae.

ECONOMIC USES:

1.Vigna mungo is an important pulse crop grown throughout India.

2.It is grown in an area of about three million hectares in India.

3.Annual production of urdbean in India is about 1.3 million tonnes.

4.It is mainly used as 'dal' and in preparation of many dishes in our diet.

5.In southern parts of the country, it is used in preparation of some special dishes.

6.It is very rich in protein containing about 25 per cent protein in its seed and is the richest in phosphoric acid among pulses.

7.Besides, this green fodder of urdbean is very nutritive and is specially useful for milch cattle.

8.It can also be used as green manure.

9.It also acts as cover crop and its deep root system protects the soil from erosion.

10.Urdbean being leguminous has the capacity to fix atmospheric nitrogen and thus helps in restoring the soil fertility.

3.GREEN GRAM (Myng bean):

Family: Fabaceae

Botanical name:      Vigna radiata

ECONOMIC USES:

1. Green gram is consumed as food in several ways. In India it is mostly used as dal along with the cereals.

2. The flour of gram is used in the preparation of biscuits, namkin, sweets and for other purpose.

3. The germination grains are consumed as nutritious food for good health.

4. The grains and plant residues are used as cattle feed.

5. This is an ideal and important crop for rotation with cereals and also used for green manuring purposes.

Oil  seeds:  mustard, groundnut,  sunflower:

1.MUSTARD (Rape seed):

Family                        :           Cruciferae

Botanical Name            :        Brassica juncea

India occupies the first position both in area and production of rape seed and mustard.

ECONOMIC USES:

1. Rape seed and mustard give edible oil which is used as cooking medium in north India.

2. Seed is used as condiment in the preparation of vegetable and curries.

3. Split seed (Mohari dal) and oil is used for pickling.

4. The leaves of the young plants are used as vegetable.

5. Oil cake is fed to cattle.

6. Oil content mustard varies from 30 to 48%.

7. Oil content of white mustard varies from 25 to 33%.

2.GROUNDNUT (Pea nut):

Botanical Name:    Arachis hypogaea I.

Family:    Papilionaceae.

ECONOMIC USES:

1. It is a creeping or bushy annual plant with a characteristic habit of ripening its fruits underground (Fig. 73).

2. The plants are used for forage and stock-feeding.

3. Nuts are used commonly in winter season as such, or in the preparation of candy or peanut butter.

4. From the seeds or nuts, peanut oil is obtained. Refined oil is used for cooking purposes, while the inferior grades are used for soap making and as illuminants.

5. The hydrogenated oil yields the ‘vegetable ghee’.

6. Oil cake is used as a stock feed for catties.

7. Ardil, a synthetic fibre, is manufactured from the proteins found in groundnuts.

8. Groundnut has high nutritive value. It is highly rich in proteins and vitamins, particularly vitamin B and nicotinic acid.

9. High quality oil is used in pharmaceutical industry.

10. Groundnut shells are used for manufacture of cork substitutes and coarse boards.

3.SUNFLOWER (Kusumbha):

Family                        :           Compositae

Botanical Name            :      Carthamus tinctorius

Safflower oil does not increase the cholesterol level in human blood and hence good for health.

ECONOMIC USES:

1. Safflower is most important rabi oilseed crop grown in Maharashtra.

2. It is grown mainly for edible oil and sometimes for dye purpose.

3. The oil is good for heart patients as it contains polyunsaturated fatty acids.

4. It is drying oil and hence used in manufacture of paints, varnishes, water proofing material, adhesives for glass etc.

5. The oil cake from decorticated seed is fed to cattle.

6. The leaves of young plants are used as vegetable.

7. Red and yellow dye obtained from the flower heads is used for colouring cloths.

8. It is grown as border crop to protect the main crop from domestic animals.

9. Dried stalks are used as fuel or for making paper.

10. Oil content of safflower is about 28 to 30 p.c.

Fibre:  cotton,  jute:

1.COTTON

Botanical Names:

Gossypium sp. (G. arboreum, G. barbadense, G. berbaceum and G. hirsutum).

Family:   Malvaceae.

ECONOMIC USES:

1. It is the chief fibre plant which supplies more than 70% of the world consumption of fibres.

2. Fibres occur on the seeds in the form of flattened, twisted and tubular hairs (Fig. 77).

3. Raw cotton consists of cellulose (94%), protein (1.3%), pectic substances (0.9% to 1.2%), water (0.6%), sugar (0.3%) and some pigment traces.

4. Chief use of the cotton is in the textile industry. Other uses include stuffing of pillows, cushions, and also in rubber tyre fabrics.

5. Short fibres, called linters or fuzz, are used for superior acetates and viscose rayons, cellulose ethers and esters, and nitrocellulose lacquers.

6. Hull, the outer covering of cotton seeds, is used for cattle feeding, fertilizers, fillers in plastics, and manufacture of insulating materials.

7. A most important semidrying oil (cotton seed oil) is obtained from the seeds of cotton. It is used as a cooking oil. Other uses of this oil include in the preparation of soaps, paints and varnishes, washing powders, artificial leather, glycerine, nitroglycerin, etc.

8. Seed cake is used as fertilizer and as cattle feed.

9. Gossypium roots are used in some fevers.

10. Its seeds are used in diseases like gonorrhoea, catarrh and gleet.

11. Leaf juice of G. berbaceum is used in scorpion and snake bites.

12. Cotton fibre is also used in paper industry, specially in preparing fine quality paper.

2. JUTE  (Hindi – Pat or Titapai):

Botanical Name:   Corcborus capsularis, C. olitorius.

Family:   Tiliaceae.

1. It is a chief fibre-yielding annual shrub.

2. Fibres are obtained from the stem of two species, i.e., C. capsularis and C. olitorius.

3. It is a bast fibre, obtained from the secondary phloem by the process of retting.

4. Jute is cultivated in West Bengal, Assam, Orissa, Bihar and U.P.

5. Jute fibre is used in making carpets, coarse material, twine, gunny bags, paper and many similar articles.

6. Jute forms the base of linoleum and wool carpet industry.

7. High quality grease-proof paper is prepared from the fibres of jute sticks. It is used commonly is confectionery industry for wrapping greasy materials.

8. Dried leaves of C. capsularis are also used as a remedy for dysentry.

9. Besides India, Bangladesh is also a chief jute- producing country of the world.

Beverages:  coffee,  tea:

1.COFFEE:

Botanical Names:

Coffea arabica (Arabian Coffee); C. canepbora syn. C. robusta (Congo Coffee); C. liberica (Liberian Coffee).

Family:   Rubiaceae

ECONOMIC USES:

1. It is an important non-alcoholic beverage, like tea.

2. More than 90% coffee is obtained from the berries (Fig. 95) of Coffea arabica.

3. Coffee beans are roasted for developing the aroma, flavour and colour and finally ground before they reach to the consumer.

4. “Beans” contain caffeine (0.75 to 1.5%), a volatile oil, glucose, dextrins, proteins and a fatty oil.

5. Caffeine provide stimulating effect while the volatile oil (caffeole) is responsible for aroma and flavour.

6. Leaves and fruits of Coffee also contain some alkaloids.

7. In India, C. arabica is grown in Nilgiris and Kamataka.

8. Seeds of C. canepbora (syn. C. robusta), a robust evergreen shrub, are used in making “instant coffee”.

2.TEA:

Botanical Name:   Camellia sinensis (L). O. Kuntze (Syn. Thea sinensis L.)

Family:   Theaceae

ECONOMIC USES:

1. It is the most common non-alcoholic beverage, used by more than one-half of the world’s population.

2. It is obtained from the dried leaves of Camellia sinensis, a native of Assam or China.

3. Tea plant is a small shrub with leathery, lanceolate leaves having serrate margin and many oil glands (Fig. 94).

4. A volatile oil, tannin (13 to 18%), and an alkaloid theine (2-5%), are present in tea.

5. Tea leaves, when infused in hot water, dissolve their alkaloid and oil, and the beverage thus resulted has a stimulating effect. If boiled for a longer period, tannin dissolves making the beverage less beneficial.

6. India is a leading tea-exporting country.

7. For preparing green tea, the leaves are steamed and dried without fermenting, while for black tea the leaves are withered, rolled, fermented and dried.

8. Tannins of tea waste are used in plywood industry.

9. Assam, Darjeeling, Nilgiris, Dehradun and Kumaon are the main tea-producing regions in India.

UNIT-(III)

NUMERICAL CHROMOSOME ABERRATION:

In some case, number of chromosome in an affected person can are increased or decreased. Following types of chromosomal abnormalities are produced due to change in chromosomal number.

(A)ANEUPLOIDY:

The random abnormal number of chromosomes in the animals is called as aneuploidy. Aneuploidy is mostly caused by non disjunction. The members of a pair of homologous chromosomes do not move apart properly during non disjunction. Therefore, the sister chromatids fail to separate at meiosis II. In these cases, one gamete receives the same type of chromosome and another receives no copy. The other chromosomes are usually distributed normally. If these abnormal gametes unite with a normal one, the offspring will have an abnormal chromosome number. It causes aneuploidy.

Fig: Non-disjunction

Types of aneuploidy:

There are following types of aneuploidy:

1.Monosomic: (2n — I):

If a chromosome is missing the aneuploidy is monosomic. Therefore, the cell has 2n — I chromosomes. Human genetic disorders arising from monosomy are:

(a)   XO (Turner syndrome)

(b)  cri du chat syndrome: It is a partial monosomy caused by a deletion of the end of the short (p) arm of chromosome 5.

(c)   I p36 Deletion Syndrome: It is a partial monosomy caused by a deletion at the end of the short (p) arm of chromosome I.

2.Disomic:

A disomy is the presence of a pair of chromosome. For diploid organisms, such as humans, it is the normal condition. For organism that are normally triploid or above, disomy is an aneuploidy. It can occur in cells that are normally haploid, such as gametes. In uniparental disomy, the disomy means two copies of the chromosome from one of the parents (with no contribution from the other parent).

3.Trisomic (2n + I):

If the chromosome is present in triplicate in the fertilized egg the aneuploid cell is called trisomic. The cell has a total of 2n + I chromokome. There are two types of trisomy:

(a) Partial trisomy: In this case, part of an extra chromosome is attached to one of the other chromosomes. Sometimes, one of the chromosomes has two copies of part of its chromosome.

(b) Mosaic trisomy: In this case, an extra chromosomal material exists in only some of the organism’s cells.

The most common types of trisomy that survive without spontaneous abortion in humans are:

• Trisomy 21 (Down syndrome)

• Trisomy 18 (Edwards syndrome)

• Trisomy 13 (Patau syndrome)

• Trisomy 9

• XXX (Triple X syndrome)

• XXY (Klinefelter’s syndrome)

• XYY (XYY syndrome)

4.Tertrasomics:

If the chromosome is present in tetrad form in the fertilized egg the aneuploid cell is called tertrasomics for that chromosome. The cell has a total of 211 + 2 chromosomes.

5.Nullisomics:

If a set of chromosome is missing the aneuploidy is nullisomics. Therefore, the cell has 2n —0 chromosomes.

Affects of aneuploidy:

Aneuploidy is produced in sperm or egg. Later it is transmitted to the zygote. Mitosis transmits the aneuploidy to all embryonic cells. Such organism may not survive. If the organism survives, it becomes abnormal. Non disjunction can also occur during mitosis. The early aneuploid condition is passed to a large number of cells by mitosis. It has greater effect on the organism.

(B)POLYPLOIDY (euploldy):

A condition in which the organisms have more than two complete sets of chromosomes is called polyploidy. The natural occurrence of polyploids in the animal kingdom is extremely rare. But polyploidy can be induced experimentally in certain animals, such as frogs and rabbits. It occurs by two ways:

1.Autopolyploidy:

Autopolyploids are polyploids in with chromosomes derived from a single species. It has two forms:

(a) Natural Autopolyploidy: Autopolyploids can arise from a

naturally occurring spontaneous genome doubling (for example potato). Bananas and apples can be found as triploid autopolyploids. The giant tree Sequoia semperviretts or Coast Redwood has a hexaploid (6n) genome. It is a autoallopolyploid (AAAABB). Cabbage is a very interesting example of a fertile allotetraploid crop.

(b) Artificial Autopolyploidy: Polyploidy can be induced in cell culture by some chemicals like colchicine. Colchicine causes chromosome doubling.

2.Allopolyploidy:

Allopolyploids are polyploids with chromosomes derived from different species. Triticale is an example of an allopolyploid. It has six chromosome sets. Four are taken from wheat (Triticum turgidum) and two are taken from rye (Secale cereale).

Types of polyploidy:

There are following types of polyploidy:

(a)Triploidy (3n): They have an extra haploid set of chromosome in each pair. It may be produced by the fertilization of an abnormal diploid egg with sperm produced by nondisjunction.

(b)Tetraploidy (4n): They have increase of one diploid set of chromosome in each pair. Sometimes, there is the failure of a 2n zygote to divide after replicating its chromosomes. Subsequent mitosis will then produce a 4n embryo.

(c)Mosaic polyploidy: It is more common than complete polyploid animals. In this case, the animals have patches of polyploidy cells.Polyploidy in humans Polyploidy also occurs in humans. But these occur much less frequently. 1 e polyploid conditions observed in humans are triploidy (69.,(XX ) and tetraploidy (92,XXXX). Additional chromosomes contain a large amount of surplus gene product. It causes multiple disease like defects of the heart and central nervous system.

Poly ploid crops:

Polyploid plants are stronger than diploids. In the breeding of crops, those plants that are stronger and tougher are selected. Thus polyploids of many crops are produced:

(a)Triploid crops: banana. apple

(b)Tetraploid crops: wheat, maize, cotton. potato, cabbage. leek. tobacco, peanut

(c)Hexaploid crops: chrysanthemum, bread wheat, oat

(d)Octaploid crops: strawberry, dahlia, pansies. sugar cane.

Some crops are found in a variety of ploidy. Apples. tulips and lilies are commonly found as both diploid and triploid. Daylilies (hemerocallist are available as either diploid or tetraploid.

Some crops are found in a variety of ploidy. Apples. tulips and lilies are commonly found as both diploid and triploid. Daylilies (hemerocallist are available as either diploid or tetraploid.

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UNIT-(II)
Economic  Botany
Cereals:  rice,  wheat and  maize:
1.RICE (Hindi – Chaval or Dbari):
Botanical Name:   Oryza sativa L.
Family:   Gramineae or Poaceae
ECONOMIC USES:
1. Rice is the chief cereal used as staple food in most of the parts of the world.
2. Its fruit is a caryopsis.
3. It is an annual grass which grows luxuriantly in deep waters.
4. The inflorescence is a long panicle with ovate or oblong spikelets.
5. Caryopsis is oblong and angular. It remains tightly enclosed in lemma and palea.
6. Grains contain a large amount of starch, fat and proteins.
7. It is also used in the preparation of many alcoholic beverages.
8. Hats are prepared from the fibres obtained from its stem.
9. Paper, mats and boards are also prepared from rice.
10. Rice-bran oil is used for soaps, cosmetics and also as an anticorrosion oil.
11. Rice husk is used for making activated carbon, sodium silicate and silicon, and also as fuel, packing material and animal feed.
12. West Bengal, Bihar and U.P. are the chief rice- producing Indian states.
2. WHEAT (Hindi – Gehun):
Botanical Name:   Triticum aestivum L. emend. Thall.
Family:   Gramineae or Poaceae
ECONOMIC USES:
1. It is a cereal crop of family Gramineae.
2. It is the most common food plant.
3. The plant attains a height of 2-5 feet.
4. The inflorescence is a spike of spikelets. The spikelets are borne of a zigzag axis.
5. The fruit is a caryopsis.
6. Each grain consists of an outer husk, the aleurone layer containing protein, the endosperm having starch, and the embryo.
7. Wheat flour is used for making bread, biscuits, cakes, pastry and other similar articles. Wheat is also used in the manufacture of beer and other alcoholic beverages.
8. Fruit contains a single endospermic seed which contains many minerals, including Mg, Mn, Cu, Fe and Zn.
9. Wheat straw is used as a fodder for catties and for seating the chairs, mattings, hats, etc.
10. Wheat straw pulp is used for preparing writing-, printing- and wrapping paper, and straw board.
11. In India, wheat is grown mainly in Punjab, U.P., Haryana, Madhya Pradesh, Maharashtra, Rajasthan and Bihar.
12. Important wheat-producing countries are U.S.A., Russia, Australia, China, India, etc.
3.MAIZE (Hindi – Makai):
Botanical Name:  Zea mays L.
Family:   Gramineae or Poaceae.
ECONOMIC USES:
1. It is an annual cereal, attaining a height of 3 to 15 feet.
2. It is the largest amongst the cereals.
3. The stem is jointed, the leaves are large and the aerial prop roots are present in addition to the well-developed fibrous root, system.
4. Flowers are of two types, i.e., terminal tassel bearing the male flowers and cob or ear bearing the female or pistillate flowers (Fig. 71).
5. Styles are long and silky.
6. Cob is covered by large number of leafy bracts.
7. The fruit is a caryopsis consisting of hull (6%), protein or aleurone layer (8 to 14%), endosperm (70%) and embryo (11%).
8. Grains are used by man as well as animals for food.
9. Corn flakes, com starch, com syrup, com oil, dextrins and industrial alcohols are some of the maize products.
pulses:  Bengal  gram,  green  gram,  black  gram:
1.BENGAL GRAM (Chick Pea):
Botanical Name          :           Cicer arientinum
Family                      :           Leguminoceae
Bengal Gram is the most important rabi pulse crop grown in India. Rank first in area as well as in production of gram.
ECONOMIC USES:
1. Tender leaves of young gram crops are used as vegetable.
2. The grain is eaten in raw or boiled as vegetable.
3. The grain is parched and eaten as futanas.
4. Dal is grounded in flour and used in preparation of Besan or Zunka, Shev, Chakli, Bhaji etc.    
5. It is also used for preparation of sweet meats like pura-poli, laddu,mysorepak, bundi, jilebi etc.
6. The malic acid (Amb) is collected from plants which have medicinal value against stomach ache.
7. The broken grains are largely fed to horse and the dried leaves and stalks are used as fodder for cattle.
8. It is a good source of protein and content 16-19% protein.
9. Germinated seeds are good source of vie-E.
2.BLACK GRAM (Urad Dal):
Botanical Name:   Vigna mungo(Linn.) Hepper.
Family:   Leguminoseae.
ECONOMIC USES:
1.Vigna mungo is an important pulse crop grown throughout India.
2.It is grown in an area of about three million hectares in India.
3.Annual production of urdbean in India is about 1.3 million tonnes.
4.It is mainly used as 'dal' and in preparation of many dishes in our diet.
5.In southern parts of the country, it is used in preparation of some special dishes.
6.It is very rich in protein containing about 25 per cent protein in its seed and is the richest in phosphoric acid among pulses.
7.Besides, this green fodder of urdbean is very nutritive and is specially useful for milch cattle.
8.It can also be used as green manure.
9.It also acts as cover crop and its deep root system protects the soil from erosion.
10.Urdbean being leguminous has the capacity to fix atmospheric nitrogen and thus helps in restoring the soil fertility.


3.GREEN GRAM (Myng bean):
Family: Fabaceae
Botanical name:      Vigna radiata
ECONOMIC USES:
1. Green gram is consumed as food in several ways. In India it is mostly used as dal along with the cereals.
2. The flour of gram is used in the preparation of biscuits, namkin, sweets and for other purpose.
3. The germination grains are consumed as nutritious food for good health.
4. The grains and plant residues are used as cattle feed.
5. This is an ideal and important crop for rotation with cereals and also used for green manuring purposes.
Oil  seeds:  mustard, groundnut,  sunflower:
1.MUSTARD (Rape seed):
Family                        :           Cruciferae
Botanical Name            :        Brassica juncea
India occupies the first position both in area and production of rape seed and mustard.
ECONOMIC USES:
1. Rape seed and mustard give edible oil which is used as cooking medium in north India.
2. Seed is used as condiment in the preparation of vegetable and curries.
3. Split seed (Mohari dal) and oil is used for pickling.
4. The leaves of the young plants are used as vegetable.
5. Oil cake is fed to cattle.
6. Oil content mustard varies from 30 to 48%.
7. Oil content of white mustard varies from 25 to 33%.

2.GROUNDNUT (Pea nut):
Botanical Name:    Arachis hypogaea I.
Family:    Papilionaceae.
ECONOMIC USES:
1. It is a creeping or bushy annual plant with a characteristic habit of ripening its fruits underground (Fig. 73).
2. The plants are used for forage and stock-feeding.
3. Nuts are used commonly in winter season as such, or in the preparation of candy or peanut butter.
4. From the seeds or nuts, peanut oil is obtained. Refined oil is used for cooking purposes, while the inferior grades are used for soap making and as illuminants.
5. The hydrogenated oil yields the ‘vegetable ghee’.
6. Oil cake is used as a stock feed for catties.
7. Ardil, a synthetic fibre, is manufactured from the proteins found in groundnuts.
8. Groundnut has high nutritive value. It is highly rich in proteins and vitamins, particularly vitamin B and nicotinic acid.
9. High quality oil is used in pharmaceutical industry.
10. Groundnut shells are used for manufacture of cork substitutes and coarse boards.

3.SUNFLOWER (Kusumbha):
Family                        :           Compositae
Botanical Name            :      Carthamus tinctorius
Safflower oil does not increase the cholesterol level in human blood and hence good for health.
ECONOMIC USES:
1. Safflower is most important rabi oilseed crop grown in Maharashtra.
2. It is grown mainly for edible oil and sometimes for dye purpose.
3. The oil is good for heart patients as it contains polyunsaturated fatty acids.
4. It is drying oil and hence used in manufacture of paints, varnishes, water proofing material, adhesives for glass etc.
5. The oil cake from decorticated seed is fed to cattle.
6. The leaves of young plants are used as vegetable.
7. Red and yellow dye obtained from the flower heads is used for colouring cloths.
8. It is grown as border crop to protect the main crop from domestic animals.
9. Dried stalks are used as fuel or for making paper.
10. Oil content of safflower is about 28 to 30 p.c.
Fibre:  cotton,  jute:
1.COTTON
Botanical Names:
Gossypium sp. (G. arboreum, G. barbadense, G. berbaceum and G. hirsutum).
Family:   Malvaceae.
ECONOMIC USES:
1. It is the chief fibre plant which supplies more than 70% of the world consumption of fibres.
2. Fibres occur on the seeds in the form of flattened, twisted and tubular hairs (Fig. 77).
3. Raw cotton consists of cellulose (94%), protein (1.3%), pectic substances (0.9% to 1.2%), water (0.6%), sugar (0.3%) and some pigment traces.
4. Chief use of the cotton is in the textile industry. Other uses include stuffing of pillows, cushions, and also in rubber tyre fabrics.
5. Short fibres, called linters or fuzz, are used for superior acetates and viscose rayons, cellulose ethers and esters, and nitrocellulose lacquers.
6. Hull, the outer covering of cotton seeds, is used for cattle feeding, fertilizers, fillers in plastics, and manufacture of insulating materials.
7. A most important semidrying oil (cotton seed oil) is obtained from the seeds of cotton. It is used as a cooking oil. Other uses of this oil include in the preparation of soaps, paints and varnishes, washing powders, artificial leather, glycerine, nitroglycerin, etc.
8. Seed cake is used as fertilizer and as cattle feed.
9. Gossypium roots are used in some fevers.
10. Its seeds are used in diseases like gonorrhoea, catarrh and gleet.
11. Leaf juice of G. berbaceum is used in scorpion and snake bites.
12. Cotton fibre is also used in paper industry, specially in preparing fine quality paper.
2. JUTE  (Hindi – Pat or Titapai):
Botanical Name:   Corcborus capsularis, C. olitorius.
Family:   Tiliaceae.
1. It is a chief fibre-yielding annual shrub.
2. Fibres are obtained from the stem of two species, i.e., C. capsularis and C. olitorius.
3. It is a bast fibre, obtained from the secondary phloem by the process of retting.
4. Jute is cultivated in West Bengal, Assam, Orissa, Bihar and U.P.
5. Jute fibre is used in making carpets, coarse material, twine, gunny bags, paper and many similar articles.
6. Jute forms the base of linoleum and wool carpet industry.
7. High quality grease-proof paper is prepared from the fibres of jute sticks. It is used commonly is confectionery industry for wrapping greasy materials.
8. Dried leaves of C. capsularis are also used as a remedy for dysentry.
9. Besides India, Bangladesh is also a chief jute- producing country of the world.
Beverages:  coffee,  tea:
1.COFFEE:
Botanical Names:
Coffea arabica (Arabian Coffee); C. canepbora syn. C. robusta (Congo Coffee); C. liberica (Liberian Coffee).
Family:   Rubiaceae
ECONOMIC USES:
1. It is an important non-alcoholic beverage, like tea.
2. More than 90% coffee is obtained from the berries (Fig. 95) of Coffea arabica.
3. Coffee beans are roasted for developing the aroma, flavour and colour and finally ground before they reach to the consumer.
4. “Beans” contain caffeine (0.75 to 1.5%), a volatile oil, glucose, dextrins, proteins and a fatty oil.
5. Caffeine provide stimulating effect while the volatile oil (caffeole) is responsible for aroma and flavour.
6. Leaves and fruits of Coffee also contain some alkaloids.
7. In India, C. arabica is grown in Nilgiris and Kamataka.
8. Seeds of C. canepbora (syn. C. robusta), a robust evergreen shrub, are used in making “instant coffee”.
2.TEA:
Botanical Name:   Camellia sinensis (L). O. Kuntze (Syn. Thea sinensis L.)
Family:   Theaceae
ECONOMIC USES:
1. It is the most common non-alcoholic beverage, used by more than one-half of the world’s population.
2. It is obtained from the dried leaves of Camellia sinensis, a native of Assam or China.
3. Tea plant is a small shrub with leathery, lanceolate leaves having serrate margin and many oil glands (Fig. 94).
4. A volatile oil, tannin (13 to 18%), and an alkaloid theine (2-5%), are present in tea.
5. Tea leaves, when infused in hot water, dissolve their alkaloid and oil, and the beverage thus resulted has a stimulating effect. If boiled for a longer period, tannin dissolves making the beverage less beneficial.
6. India is a leading tea-exporting country.
7. For preparing green tea, the leaves are steamed and dried without fermenting, while for black tea the leaves are withered, rolled, fermented and dried.
8. Tannins of tea waste are used in plywood industry.
9. Assam, Darjeeling, Nilgiris, Dehradun and Kumaon are the main tea-producing regions in India.
UNIT-(III)
NUMERICAL CHROMOSOME ABERRATION:
In some case, number of chromosome in an affected person can are increased or decreased. Following types of chromosomal abnormalities are produced due to change in chromosomal number.
(A)ANEUPLOIDY:
The random abnormal number of chromosomes in the animals is called as aneuploidy. Aneuploidy is mostly caused by non disjunction. The members of a pair of homologous chromosomes do not move apart properly during non disjunction. Therefore, the sister chromatids fail to separate at meiosis II. In these cases, one gamete receives the same type of chromosome and another receives no copy. The other chromosomes are usually distributed normally. If these abnormal gametes unite with a normal one, the offspring will have an abnormal chromosome number. It causes aneuploidy.
Fig: Non-disjunction
Types of aneuploidy:
There are following types of aneuploidy:
1.Monosomic: (2n — I):
If a chromosome is missing the aneuploidy is monosomic. Therefore, the cell has 2n — I chromosomes. Human genetic disorders arising from monosomy are:
(a)   XO (Turner syndrome)
(b)  cri du chat syndrome: It is a partial monosomy caused by a deletion of the end of the short (p) arm of chromosome 5.
(c)   I p36 Deletion Syndrome: It is a partial monosomy caused by a deletion at the end of the short (p) arm of chromosome I.
2.Disomic:
A disomy is the presence of a pair of chromosome. For diploid organisms, such as humans, it is the normal condition. For organism that are normally triploid or above, disomy is an aneuploidy. It can occur in cells that are normally haploid, such as gametes. In uniparental disomy, the disomy means two copies of the chromosome from one of the parents (with no contribution from the other parent).
3.Trisomic (2n + I):
If the chromosome is present in triplicate in the fertilized egg the aneuploid cell is called trisomic. The cell has a total of 2n + I chromokome. There are two types of trisomy:
(a) Partial trisomy: In this case, part of an extra chromosome is attached to one of the other chromosomes. Sometimes, one of the chromosomes has two copies of part of its chromosome.
(b) Mosaic trisomy: In this case, an extra chromosomal material exists in only some of the organism’s cells.
The most common types of trisomy that survive without spontaneous abortion in humans are:
• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)
• Trisomy 9
• XXX (Triple X syndrome)
• XXY (Klinefelter’s syndrome)
• XYY (XYY syndrome)
4.Tertrasomics:
If the chromosome is present in tetrad form in the fertilized egg the aneuploid cell is called tertrasomics for that chromosome. The cell has a total of 211 + 2 chromosomes.
5.Nullisomics:
If a set of chromosome is missing the aneuploidy is nullisomics. Therefore, the cell has 2n —0 chromosomes.
Affects of aneuploidy:
Aneuploidy is produced in sperm or egg. Later it is transmitted to the zygote. Mitosis transmits the aneuploidy to all embryonic cells. Such organism may not survive. If the organism survives, it becomes abnormal. Non disjunction can also occur during mitosis. The early aneuploid condition is passed to a large number of cells by mitosis. It has greater effect on the organism.
(B)POLYPLOIDY (euploldy):
A condition in which the organisms have more than two complete sets of chromosomes is called polyploidy. The natural occurrence of polyploids in the animal kingdom is extremely rare. But polyploidy can be induced experimentally in certain animals, such as frogs and rabbits. It occurs by two ways:
1.Autopolyploidy:
Autopolyploids are polyploids in with chromosomes derived from a single species. It has two forms:
(a) Natural Autopolyploidy: Autopolyploids can arise from a
naturally occurring spontaneous genome doubling (for example potato). Bananas and apples can be found as triploid autopolyploids. The giant tree Sequoia semperviretts or Coast Redwood has a hexaploid (6n) genome. It is a autoallopolyploid (AAAABB). Cabbage is a very interesting example of a fertile allotetraploid crop.
(b) Artificial Autopolyploidy: Polyploidy can be induced in cell culture by some chemicals like colchicine. Colchicine causes chromosome doubling.
2.Allopolyploidy:
Allopolyploids are polyploids with chromosomes derived from different species. Triticale is an example of an allopolyploid. It has six chromosome sets. Four are taken from wheat (Triticum turgidum) and two are taken from rye (Secale cereale).
Types of polyploidy:
There are following types of polyploidy:
(a)Triploidy (3n): They have an extra haploid set of chromosome in each pair. It may be produced by the fertilization of an abnormal diploid egg with sperm produced by nondisjunction.
(b)Tetraploidy (4n): They have increase of one diploid set of chromosome in each pair. Sometimes, there is the failure of a 2n zygote to divide after replicating its chromosomes. Subsequent mitosis will then produce a 4n embryo.
(c)Mosaic polyploidy: It is more common than complete polyploid animals. In this case, the animals have patches of polyploidy cells.Polyploidy in humans Polyploidy also occurs in humans. But these occur much less frequently. 1 e polyploid conditions observed in humans are triploidy (69.,(XX ) and tetraploidy (92,XXXX). Additional chromosomes contain a large amount of surplus gene product. It causes multiple disease like defects of the heart and central nervous system.
Poly ploid crops:
Polyploid plants are stronger than diploids. In the breeding of crops, those plants that are stronger and tougher are selected. Thus polyploids of many crops are produced:
(a)Triploid crops: banana. apple
(b)Tetraploid crops: wheat, maize, cotton. potato, cabbage. leek. tobacco, peanut
(c)Hexaploid crops: chrysanthemum, bread wheat, oat
(d)Octaploid crops: strawberry, dahlia, pansies. sugar cane.
Some crops are found in a variety of ploidy. Apples. tulips and lilies are commonly found as both diploid and triploid. Daylilies (hemerocallist are avail
lable as either diploid or tetraploid.
Some crops are found in a variety of ploidy. Apples. tulips and lilies are commonly found as both diploid and triploid. Daylilies (hemerocallist are available as either diploid or tetraploid.

THYROID GLAND

THYROID GLAND:

Origin of Thyroid Gland:

It develops from the endoderm of the embryo.

Location and Structure of Thyroid Gland:

The thyroid gland is the largest endocrine gland located anterior to the thyroid cartilage of the larynx in the neck. The gland is well supplied with blood vessels. It is bilobed organ. The two lobes are connected by a narrow structure called the isthmus. The microscopic structure of the thyroid gland shows thyroid follicles com¬posed of cubical epithelium and filled with a homogenous material called colloid.

Small amount of loose connective tissue forms stroma of the gland. Besides containing blood capillaries, the stroma contains small clusters of specialized Para follicular cells or ‘C’ cells. The thyroid gland is the only gland that stores hormones in large quantities for about two months.

Hormones of Thyroid Gland:

The thyroid gland secretes three hormones. Thyroxine (tetraiodothyronine or T4), and tri¬iodothyronine or T3 are secreted by the thyroid follicular cells. Thyrocalcitonin is secreted by the С-cells of the thyroid gland. This gland is stimulated to secrete its hor¬mones by thyroid stimulating hormone (also called thyrotropin) secreted by the anterior lobe of pituitary gland.

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THYROID GLAND

(i) Thyroxine (T4) and Tri¬iodothyronine (T3):

T4 and T3 contain four and three atoms of iodine respectively, there¬fore, they are named so. T3 is secreted in smaller amounts but it is more active and several times more potent than T4. T4 is converted to T3 by removal of one iodine in the liver, kidneys and some other tissues. Since both T4 and T3have similar effects on the target cells, they are generally con-sidered together under the name, thyroid hormone (TH).