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1. The ABO blood types are determined by three alleles of a single gene: IA resu

ID: 133028 • Letter: 1

Question

1. The ABO blood types are determined by three alleles of a single gene: IA results in the A blood type, IB- results in the B blood type, IA IB results in the AB blood type and ii results in the O blood type. The H gene encodes the H substance that connects the A and B sugars to the surface of red blood cells and therefore hh people exhibit the O blood type. The I and H genes are on different chromosomes. A man and a woman with the following genotypes decide to have a child: I A i Hh X IB i Hh What is the probability that their first child will have blood type B?

A. 1/4 B. 1/16 C. 7/16 D. 9/16 E. 3/16

Explanation / Answer

Answer is C. By plotting the table of cross between the gamete combinations (IA, i, H, h) and (IB, i, H, h); there will be 7 cases of B blood group in which it is considered that H code for A or B blood group. So probability of B blood group is 7/16.