Question

In a random mating population the frequency of dominant alleles is 0.7. what will be the frequency of homozygous dominant phenotype.
A) 0.49
B) 0.09
C) 0.3
D) 0.21

Answer 1

Hint:Random mating is an expression in population genetics. It describes an perfect situation in which all individuals on one sex are equally possible partners of all members of the opposite sex. The technical term for this is panmixia.

Complete answer:
Random mating refers to matings in a population that take place in amount to their genotypic frequencies. For instance, if the genotypic frequencies in a population are MM=0.83, MN=0.16 and NN=0.01 then we would be expecting that 68.9% $(0.83 \times 0.83 \times 100)$ of the matings would occur among MM individuals. If a significant divergence from this expected value occurred, then random mating did not go off in this population. If significant deviations occurred in the other matings [for example $(MM \times MN or MN \times NN)$], again the assumption of random mating will have been violated.

In humans, as a minimum, for many characteristics such as blood type, random mating will occur. Individuals do not intentionally select a mate according to blood type. But for other traits, such as intelligence or physical build up , this is the case. For these characters the population is not random mating. But this does not prevent the analysis of the population for those traits at which random mating is occurring.

In a population at balance, mating must be random. In assortative mating, individuals are inclined to choose mates similar to themselves. For example, large blister beetles tend to prefer mates of large size and small blister beetles tend to choose small mates.

In accordance with the question, the genotype frequency of the dominant allele is p = 0.7. While p+q = 1; thus the frequency of recessive allele = q = 1-0.7 = 0.3. The frequency of recessive phenotype = q2 = 0.09.

Therefore the correct answer is option (B) 0.09


Note: Random mating is generally an expression which is used in population genetics. Another term which is used for population genetics is panmixia. And considering the above condition the correct answer for this question is 0.09.