Final answer:
Alleles are alternative forms of a gene that occupy corresponding positions on homologous chromosomes. Genes determine specific characteristics by coding for specific proteins. Different alleles can result in different traits.
Step-by-step explanation:
Alleles are alternative forms of a gene that govern the same feature, such as eye color, and occupy corresponding positions on homologous chromosomes. Homologous chromosomes are the matched pairs of chromosomes in a diploid organism that have the same genes in the same location. Genes, which are the functional units of chromosomes, determine specific characteristics by coding for specific proteins. Different versions of genes, called alleles, can result in different traits.