Question

In a population of $1000$ individuals $360$ belong to genotype AA, $480$ to Aa, and the remaining $160$ to aa. Based on the data, the frequency of allele A in the population is
A. $160$
B. $0.5$
C. $0.6$
D. $0.7$

Answer 1

An allele is one of two or more variants of a given gene. The ABO blood classification, for example, is dominated by the ABO gene, which has six common alleles. About every living human's ABO gene-phenotype is a combination of these six alleles.

Complete answer:
The Hardy-Weinberg equilibrium is a theory that states that in the absence of disturbing causes, genetic diversity in a population will remain constant from generation to generation. By adding new alleles into a group, mutants, for example, disturb the balance between allele frequencies.
According to Hardy-Weinberg equilibrium,
${p^2}\; + 2pq{\text{ }} + {\text{ }}{q^{2\;}} = {\text{ }}1$
where ${p^2}$ represents the frequency of homozygous genotype AA
The frequency of genotype aa is denoted by ${q^2}$.
The occurrence of genotype Aa is denoted by pq.

There are $1000$ people, $360$ of whom are of genotype AA.
${p^2} = \dfrac{360}{1000} = 0.36$
Then $p{\text{ }} = {\text{ }}0.6$

Hence the correct option is C ($0.6$).

Additional information:
The Hardy–Weinberg theory is based on certain assumptions:
(1) Mating at random (i.e, population structure is absent and matings occur in proportion to genotype frequencies).
(2) A lack of natural selection.
(3) A sizable population scale (i.e., genetic drift is negligible).
(4) There is no gene flow or migration.
(5) There is no mutation.
(6) The locus is autosomal dominant.
Deviations from Hardy–Weinberg proportions will occur where certain assumptions are broken.

Note: The Hardy-Weinberg model allows one to relate the genetic structure of a population over time to the genetic structure we would predict if the population were in Hardy-Weinberg equilibrium (i.e., not evolving).
- If genotype frequencies vary from those expected under equilibrium, we can conclude that one or more of the model's assumptions is being violated and try to figure out which one (s).
- Looking at allele and genotype frequencies in allozymes is one approach to studying genetic diversity. Allozymes are enzymes that travel at varying concentrations in gel electrophoresis due to the presence of several alleles at a single locus.