Question

In Mendelian genetics, a dominant allele is:

a. a better fit
b. more common
c. the one that is expressed phenotypically over other alleles
d. the one that codes for the normal expression of a trait

Answer 1

In Mendelian genetics, a dominant allele is the one that is expressed in the phenotype over other alleles, regardless of whether the individual is homozygous or heterozygous for the gene.

Explanation:

In Mendelian genetics, a dominant allele is the one that is expressed phenotypically over other alleles. For example, if an individual inherits one allele for blood type A (dominant) and one for blood type O (recessive), the person will exhibit blood type A. Individuals with two identical alleles (AA or OO) are homozygous, and those with one of each (Aa) are heterozygous. However, the dominant trait, in this case blood type A, is observed phenotypically in both homozygous dominant (AA) and heterozygous (Aa) individuals. It's important to note that dominance does not necessarily mean that an allele is better or more common; it is purely an expression pattern. In some cases, mutant alleles can show dominance over the wild type, as is seen with the Antennapedia mutation in Drosophila, where the mutant allele causes legs to grow in the place of antennae on the head.