What feature distinguishes a heterozygous individual from a homozygous individual?

A heterozygous individual is characterized by having two different alleles for a specific gene. This can occur when one allele is inherited from one parent and a different allele is inherited from the other parent. For example, if the alleles for a particular trait are A and a, an individual with one A allele and one a allele is considered heterozygous (Aa).

This genetic configuration allows for greater variation in traits and can influence the phenotype displayed by the organism, especially if one allele is dominant over the other. In contrast, a homozygous individual has two identical alleles for that gene, which could be either two dominant or two recessive alleles (AA or aa). Therefore, the presence of two different alleles distinctly defines a heterozygous condition, setting it apart from homozygosity.

This distinction is fundamental in genetics, affecting how traits are expressed and inherited.