An Organism That Has Only One Copy of a Gene

Question

An organism that has only one copy of a gene is called a:
A) Heterozygote
B) Homozygote
C) Hemizygote
D) Zygote
E) None of these

Accepted Answer

A hemizygote is an organism that has only one allele (copy) of a gene. This typically occurs in males for genes located on the X chromosome, as they only have one X chromosome. Heterozygotes have two different alleles for a gene, while homozygotes have two of the same allele. The term zygote refers to a single-celled organism formed by the fusion of gametes (sperm and egg). Therefore, the correct answer is hemizygote.