Humber Admissions Practice Test

What does 'homozygous dominant' mean?

1. Two different alleles for a trait

2. Two identical alleles that are recessive

3. Two identical alleles that are dominant

4. One dominant and one recessive allele

The correct answer is: Two identical alleles that are dominant

The term 'homozygous dominant' refers to having two identical alleles for a particular trait, both of which are dominant. In genetics, alleles are variations of a gene that can lead to different traits. When an individual is homozygous for a dominant allele, it means that there are no contrasting forms of the gene present; instead, the same dominant allele is inherited from both parents. This is significant because it determines how the trait is expressed in the organism. In cases of homozygosity, the dominant traits will be fully expressed, without being masked by any recessive traits. For instance, if the allele for dark hair is dominant, an individual who is homozygous dominant for dark hair will have dark hair, as both alleles contribute to this trait. The other descriptions pertain to different genetic configurations: having two different alleles represents heterozygous conditions; two recessive alleles indicate a homozygous recessive state; and one dominant and one recessive allele indicates a heterozygous arrangement. These variations demonstrate the complexity of genetic inheritance and the relationships between different alleles.