Mendelian Link Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

The likelihood of a dominant trait being expressed in a phenotype is best described by the concept of penetrance. Penetrance refers to the percentage of individuals with a specific genotype (in this case, one that carries a dominant allele) who actually express the corresponding phenotype. For instance, if a dominant allele is present but not all individuals show the dominant trait, this indicates incomplete penetrance. This concept is especially relevant in cases where certain genes may not always lead to observable traits due to various factors, including environmental influences or interactions with other genes.

In contrast, expressivity relates to the degree or intensity with which a genotype is expressed in a phenotype, which can vary among individuals carrying the same genotype. Phenotypic ratio refers to the proportion of different phenotypes produced by a specific genetic cross and is used primarily in genetic predictions. Genotype frequency pertains to the relative frequency of a particular genotype in a population rather than the expression of traits. Hence, penetrance accurately captures the essence of how likely it is for a dominant trait to be seen in an individual's phenotype.