Final answer:
Alleles are alternative versions of the same gene that can result in variations of a trait or characteristic. A diploid organism can be homozygous or heterozygous for a gene.
Step-by-step explanation:
Alleles are alternative versions of the same gene. They are different forms of a gene that can result in variations of a trait or characteristic. A diploid organism can be homozygous, meaning it has two identical alleles for a gene, or heterozygous, meaning it has two different alleles for a gene.