# evolution

• ans-4 pls explain

• @sri
The actual frequency calculations depend on the ploidy of the species for autosomal genes.

Haploids
Edit
The frequency (p) of an allele A is the fraction of the number of copies (i) of the A allele and the population or sample size (N), so

p = i/N.
Diploids
Edit
If {\displaystyle f(\mathbf {AA} )} f(\mathbf{AA}), {\displaystyle f(\mathbf {AB} )} f(\mathbf{AB}), and {\displaystyle f(\mathbf {BB} )} f(\mathbf{BB}) are the frequencies of the three genotypes at a locus with two alleles, then the frequency p of the A-allele and the frequency q of the B-allele in the population are obtained by counting alleles.

{\displaystyle p=f(\mathbf {AA} )+{\frac {1}{2}}f(\mathbf {AB} )={\mbox{frequency of A}}} p=f(\mathbf{AA})+ \frac{1}{2}f(\mathbf{AB})= \mbox{frequency of A}
{\displaystyle q=f(\mathbf {BB} )+{\frac {1}{2}}f(\mathbf {AB} )={\mbox{frequency of B}}} q=f(\mathbf{BB})+ \frac{1}{2}f(\mathbf{AB})= \mbox{frequency of B}
Because p and q are the frequencies of the only two alleles present at that locus, they must sum to 1. To check this:

{\displaystyle p+q=f(\mathbf {AA} )+f(\mathbf {BB} )+f(\mathbf {AB} )=1} p+q=f(\mathbf{AA})+f(\mathbf{BB})+f(\mathbf{AB})=1
{\displaystyle q=1-p} q=1-p and {\displaystyle p=1-q} p=1-q
If there are more than two different allelic forms, the frequency for each allele is simply the frequency of its homozygote plus half the sum of the frequencies for all the heterozygotes in which it appears.

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