What is the difference between heterozygous and homozygous alleles?

The distinction between heterozygous and homozygous alleles is fundamental in genetics. Heterozygous refers to an individual having two different alleles for a specific gene, which means that the genetic makeup includes one dominant and one recessive allele, or two different variants of a gene. This condition can lead to a range of phenotypic expressions because the interaction between the two different alleles may affect the trait being expressed.

On the other hand, homozygous describes an individual with two identical alleles for a specific gene. This means both alleles are the same, whether they are both dominant or both recessive. In this scenario, the trait expressed will be a direct reflection of the single type of allele present.

Understanding these definitions helps clarify concepts like dominance and phenotype expression. In heterozygous individuals, the dominant allele often masks the effect of the recessive allele, while homozygous individuals can express either a dominant or recessive trait based purely on the two identical alleles present. This knowledge is vital for predicting inheritance patterns and understanding genetic diversity within a population.