The A-B-O blood types are determined by three alleles r^A, r^B, and i. In a rand
ID: 83557 • Letter: T
Question
The A-B-O blood types are determined by three alleles r^A, r^B, and i. In a randomly mating population the frequency of individuals who are homozygous for type A blood is 0.2, the frequency of individuals who are homozygous for type B blood is 0.1, and the frequency of individuals are blood type O is 0.25. What is the frequency of individuals that are blood type AB? A) 0.141 B) 0.122 C) 0.273 D) 0.061 E) 0.082 In a sample of 1000 individuals (700 men and 300 women) 52 men have X-linked colour blindness (X^c) and all the others have normal colour vision (X^c). What is the frequency of women who are carriers? A) 0.12 B) 0.88 C) 0.14 D) 0.02 E) 0.21 Selection that favours extreme values of a trait and not intermediate values is known as: A) Stabilizing selection B) Disruptive selection C) Directional selection D) Directional selection and Disruptive selection E) All of theseExplanation / Answer
Answer 1 = 0.141
Lets assume that p is the frequency of IA , q is the frequency of IB and r is the frequency of i such that p+q+r = 1
Under Hardy Weinberg equilibrium, allelic frequency is equal to square of genotypic frequency.
Here p2 = 0.2 , q2 = 0.1 and r2 = 0.25
Therefore p = 0.447 , q = 0.316 , r = 0.5
Now people carrying the AB blood type would have IAIB as their genotype. Therefore the frequency of individuals carrying this blood type are = (p*q) = 0.1412
Answer 2 = 0.21
Out of 700 men 52 have X linked colour blindness, therefore
648 men will have XY and 52 will have XcY combination
(52/700)* 100 = 7.4% males are colour blind.
Therefore q = 0.074; q2 = (0.074)2 = 0.005
Now q = 0.21
Answer 3
Selection that favours extreme values of a trait is known as disruptive selection. Intermediates are not selected. In this kind of selection variance increases and the population divides into two distinct groups.
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