Humber Admissions Practice Test

Which term describes an organism that has two different alleles for a trait?

1. Homozygous dominant

2. Heterozygous

3. Homozygous recessive

4. Dominant allele

The correct answer is: Heterozygous

The term that describes an organism possessing two different alleles for a trait is heterozygous. This indicates that the organism has one allele that may express a dominant trait and another that may express a recessive trait. The presence of these different alleles means that the organism can exhibit variations in expression of that particular trait, depending on the dominance relationship between the alleles. In contrast, homozygous dominant refers to an individual with two identical dominant alleles for a trait, which means there is no variation in the alleles present. Homozygous recessive describes an organism with two identical recessive alleles for a trait, again showing no variation. Dominant allele is simply a term that refers to one form of an allele that can mask the expression of another, rather than describing the genetic combination of the organism itself. Thus, heterozygous is the correct term that encapsulates the situation of having two different alleles.