Ace the HOSA Human Heredity Challenge 2026 – Decode Your Path to Success!

When an organism possesses two identical alleles for a particular gene, it is described as homozygous. This means that both alleles, one inherited from each parent, are the same. For example, if an organism has two alleles for a trait that are both dominant, such as AA, or two that are both recessive, such as aa, it is considered to be homozygous for that gene.

In contrast, heterozygous describes a situation where an organism has two different alleles for a gene, presenting a combination such as Aa. Hemizygous refers to the condition where an organism has only one allele for a particular gene, often seen in males for genes located on the X chromosome due to the presence of only one X chromosome. Finally, diploid refers to the total number of chromosomes in an organism's cells, meaning it has two complete sets of chromosomes, but it does not specify the identity of the alleles for a particular gene. Therefore, the key concept of identical alleles is encapsulated clearly in the term homozygous.