What does it mean when two alleles are heterozygous?

When two alleles are described as heterozygous, it means that the two alleles at a specific locus on a chromosome are different from each other. This genetic variation can result in a mix of traits, as one allele may be dominant over the other. For example, if one allele codes for tall plants and the other for short plants, the plant will exhibit the dominant trait, which in this case is height.

Understanding the heterozygous condition is important in genetics because it influences the phenotypic expression of traits in an organism. The presence of different alleles can enhance diversity within a species, affecting its adaptability and evolution. Thus, when alleles are heterozygous, they bring about contrasting traits as each allele contributes differently to the organism's phenotype.