Humber Admissions Practice Test

What does 'homozygous recessive' indicate?

1. Two dominant alleles are present

2. Two recessive alleles are present

3. One allele is dominant, and the other is recessive

4. There is no dominant allele present

The correct answer is: Two recessive alleles are present

The term 'homozygous recessive' indicates the presence of two identical alleles for a particular trait, specifically both being recessive. This means that the individual carries two copies of the recessive allele, which can manifest in the phenotype only when no dominant allele is present. In genetics, alleles are variants of a gene that can determine traits. A dominant allele masks the effect of a recessive allele when both are present; however, if an organism is homozygous recessive, it means that neither of the alleles is dominant, thus expressing the recessive trait. This is a fundamental concept in Mendelian inheritance, allowing us to predict the inheritance patterns of traits. The other choices reference combinations of dominant and recessive alleles which do not apply in this case. The focus on having two recessive alleles makes the understanding of homozygous recessive clear, illustrating that such a genotype leads to the expression of the recessive phenotype when no dominant alleles are present.