A genotype is described as heterozygous when it contains two different alleles for a particular gene.

For example:

* Bb - This genotype is heterozygous for the gene "B", with one dominant allele (B) and one recessive allele (b).

Here are some other examples of heterozygous genotypes:

* Aa

* Dd

* Rr

* Yy

Important note: Heterozygous genotypes are different from homozygous genotypes, which have two identical alleles for a gene (e.g., BB, bb, AA, aa).