Short Answer Type
Long Answer Type(a) What is polygenic inheritance ? Explain with the help of a suitable example.
(b) How are pleiotropy and Mendelian pattern of inheritance different from polygenic pattern of inheritance ?
Short Answer TypeGive an example of an autosomal recessive trait in humans. Explain its pattern of inheritance with the help of a cross.
Long Answer TypeDescribe the mechanism of pattern of inheritance of ABO blood groups in humans.
In humans, the ABO blood groups are controlled by a gene called I gene. It has three alleles, namely IA, IB and i. A person possesses any two of the three alleles. IA and IB dominate over i. But with each other, IA and IB are co-dominant that is they both get expressed when present together.
IA and IB are responsible for the production of antigen A and B present on the surface of RBC. Plasma membrane of RBC possess sugar polymer that protrudes out of its surface and the type of sugar present on the surface is controlled by gene I. IA and IB allele is responsible for coding for glycosyltransferase enzyme responsible for developing modification in the terminal sugar molecule. IA and IB differ very minutely on the sugar molecule while gene i does not produce any sugar molecule. Here allele A and B are dominant in nature while ii fail to produce any antigenic molecule so express blood group O. 
A. Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.
B. A pregnant human female was advised to undergo M.T.P. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX egg fertilized by Y-carrying sperm. Why was she advised to undergo M.T.P.?
Short Answer TypeDuring a medical investigation, an infant was found to possess an extra chromosome 21. Decribe the symptoms the child is likely to develop later in the life.
Long Answer TypeState and explain the ‘law of independent assortment’ in a typical Mendelian dihybrid cross.
Short Answer TypeGive a scientific term:
Exhibition of superiorityof the hybrid over both of its parents
Switch
