The answer is: the number of different alleles in a population.
So let’s do an example:
Allele frequency tells you how common (frequent) an allele is.
An allele is a version of a gene.
let’s say theres a gene (instruction) for eye colour. And We can make different types of eyes.
brown, green, blue.
So we can say the gene (instructions) has 3 alleles (3 variations)
If you have an high allele frequency for the brown allele in group A. It means that brown eyes are super common in group a.
Now It can get a little complicated and the details are not needed for this question. if you want an slightly more in-depth explanation but I’ve added a little detail bellow:
There are three things that can happen in genetics.
1) You can have an allele for brown eyes and have brown eyes, (it shows in your phenotype)
2) You can have the allele for brown eyes and NOT have brown eyes (it doesn’t get expressed so it doesn’t show up in the person). Here you have the genetic code for it but you don’t express it. It doesn’t actually show up so you end up with blue eyes or something.
or
3) you can not have the allele for brown eyes so it’s not in your genetics and it doesn’t show up in your phenotype.
If there. Is a high allele frequency for brown eyes. It means that we analysed the genetic code of everyone in group A and found that a lot of people in this group have the allele for brown eyes EVEN the people who don’t show brown eyes in their phenotype.
If this is a little confusing please don’t worry you don’t need this level of detail to understand this question.
The answer for this question is: the number of different alleles in a population.