Question

Given what we know about the relationship between genes, chromosomes, and DNA, why can more than one allele of a gene be present in an indívidual?

Group of answer choices

Because recessive alleles need to be in the presence of another recessive to show their phenotype

This cannot happen; there can be many alleles for a gene, but most organisms will carry only one of them

Most eukaryotic organisms have at least 2 sets of homologous chromosomes

Due to blending inheritance, organisms will combine alleles that they inherit from their parents

Answer 1

Eukaryotic organisms have two sets of homologous chromosomes. These are known as diploid organism. They inherit one set of homologous chromosomes from each parent that increases the diversity. Each gene has two alleles which can be either dominant or recessive. One allele of a gene is present on each set of homologous chromosome. If the alleles are identical, then the organism is homozygous for that allele- whether dominant or recessive. If they inherit one allele of each type, they are heterozygous organism.

Recessive alleles can be co-dominant as well and need not be always in two copies to be inherited. If the recessive gene is present in X chromosome, one allele is sufficient to cause phenotype in the males. Most organisms are diploid and hence carry two alleles of a gene. Alleles are combined for inheritance of phenotypes. This combination occurs at fertilization of male and female gametes. However, they are not the reason why individual have more than one allele.

Right choice: Most eukaryotic organisms have at least 2 sets of homologous chromosomes.