Question

Why can only 2 alleles be present in any individual?

Answer 1

There may be many possible alleles for any gene, but a diploid cell or animal contains only two alleles of each gene or two copies of a single allele; a haploid gamete contains one copy of each gene, so only one allele.Since diploid organisms have two copies of each chromosome, they have two of each gene. Since genes come in more than one version, an organism can have two of the same alleles of a gene, or two different alleles. This is important because alleles can be dominant, recessive, or codominant to each other.