What does it mean for an individual to be heterozygous?

What does it mean for an individual to be heterozygous?

• A. An individual with two identical alleles for a trait
• B. An individual with only one allele for a trait
• C. An individual that has two different alleles for a trait
• D. An individual with no alleles for a trait

Answer: (C)

Being heterozygous means you carry two different versions of a gene at the same place on the paired chromosomes. For example, one chromosome might have the A allele and the other the a allele, giving a genotype like Aa. This is different from having two identical alleles (AA or aa), which is homozygous for that trait. In a diploid organism, you usually have two copies of each gene, and the combination you carry determines the genotype, while the phenotype often reflects the dominant allele present. The options describing two identical alleles, only one allele, or no alleles don’t fit this idea, whereas two different alleles correctly capture what heterozygous means.

Being heterozygous means you carry two different versions of a gene at the same place on the paired chromosomes. For example, one chromosome might have the A allele and the other the a allele, giving a genotype like Aa. This is different from having two identical alleles (AA or aa), which is homozygous for that trait. In a diploid organism, you usually have two copies of each gene, and the combination you carry determines the genotype, while the phenotype often reflects the dominant allele present. The options describing two identical alleles, only one allele, or no alleles don’t fit this idea, whereas two different alleles correctly capture what heterozygous means.