Which term describes having two different alleles for a given gene?

Which term describes having two different alleles for a given gene?

• A. Heterozygous
• B. Homozygous
• C. Monoallelic
• D. Hemizygous

Answer: (A)

Having two different alleles at the same gene locus defines a heterozygous state. Each person carries two alleles for every gene, one from each parent, and when those two alleles differ (for example, A and a), the genotype is heterozygous. If the two alleles are the same (AA or aa), that’s homozygous. Monoallelic usually refers to situations where only one allele is expressed or present for a gene in a cell, not two different ones, and hemizygous means having only one allele at a locus in a diploid organism (as with genes on the X chromosome in many males). So, the term that describes having two different alleles is heterozygous.

Having two different alleles at the same gene locus defines a heterozygous state. Each person carries two alleles for every gene, one from each parent, and when those two alleles differ (for example, A and a), the genotype is heterozygous. If the two alleles are the same (AA or aa), that’s homozygous. Monoallelic usually refers to situations where only one allele is expressed or present for a gene in a cell, not two different ones, and hemizygous means having only one allele at a locus in a diploid organism (as with genes on the X chromosome in many males). So, the term that describes having two different alleles is heterozygous.