Notes

Heredity:
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Chromosome:
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- The main heredity material is chromosome.
- Scientist Strasburger in 1875 first discovered chromosome.
- In different species, the number of chromosome pairs may be from 2 to 1600.
- In length, a chromosome might be from 3.5-30.00 micron
- In width, a chromosome might be 0.2 to 2.0 micron.
- Main function of chromosome is to carry genes.
- Chromosomes are designated as the physical basis of heredity.

DNA:
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- Main component of chromosome is DNA
- Deoxyribonucleic Acid
- Double stranded spiral structure
- It is composed of 5 carbon sugars, inorganic phosphate and nitrogen bases (thymine, guanine, cytosine, adenine)
- Nitrogen bases are of two types:
(1) Purine (2) Pyrimidine
- Adenine and guanine are purines and thymine and cytosine are pyrimidines.
- Adenine of a strand connects with the thymine of another strand by two hydrogen bonds
- Guanine of a helix connects with the cytosine of another helix by three hydrogen bonds

RNA:
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- Ribonucleic Acid
- Composed of 5 carbon sugars, inorganic acid, nitrogen bases (adenine, guanine, cytosine, uracil)
- Viruses which do not have DNA use RNA as their nucleic acid.

Determination of human sex:
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- There are 23 pairs of chromosomes in the body. 22 of the pairs are used for heredity and physical basis. However the last pair is the sex chromosome.
- The sex chromosome in males contain X,Y chromosome
- The sex chromosome in females contain X,X chromosome
- During egg fertility, meiosis occurs and the X chromosome from mother possesses another chromosome from the father.
- Here, during formation of sperm, half of them contain X chromosome and the other half contain Y chromosome.
- The egg becomes fertilized by the sperm of either of the chromosomes of X or Y.
- The egg becomes a zygote with the formation through X,X or X,Y.
- If it is X,X then its a girl
- If it is X,Y then its a boy

Color Blindness:
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- Hereditary disease
- There are pigments in the optical nerve cells of eyes
- If there is a lack of 1 pigment in the optical nerve, then the person can not differentiate between red and green
- If there is a lack of more than 1 pigment, then the person can not differentiate between blue and yellow.

Thalassemia:
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- The hereditary disease which involves the disintegration of abnormal state of red blood cells
- Every year, 7000 babies are born with thalassemia.
- Present number of thalassemia patients are one lakh
- Red Blood Cells are composed of two proteins:
(1) a globulin (2) B globulin
- Thalassemia occurs if the genes for the production of a globulin of red blood cells are missing and thus, disintegration of red blood cells occur.
- Again if the genes for the production of B globulin is missing, then the disintegration of red blood cells also occur.
- There are 2 types of Thalassemia:
(1) Major (2) Minor
- Major thalassemia is when both parents have thalassemia and it is passed down to the child
- Minor is when only one parent has it.
- It is treated by blood transfusion in a regular basis.
- The thalassemia patient must not eat iron based food.