Simplify the following text for a Grade 10 native English-speaking person.
Original: For example , if the frequency of an allele is 20 % in a given population , then among population members , one in five chromosomes will carry that allele .
Simplified: Allele frequencies may be used to describe genetic diversity in a population . If the frequency of any allele is above 1 % it is probable that natural selection is maintaining it at this level .