Did any alleles disappear from your population? if so, why? if not, why not? how does this relate to the most fit phenotype

Alleles can disappear from a population through natural selection. This relates to the most fit phenotype because the breed with the desirable trait, or the most fit, will live and produce off spring. Eventually the less desirable trait and its corresponding allele will disappear after multiple generations pass. If the environment does not change alleles of non desirable traits will disappear.