What is a dominant allele?

A dominant allele is defined as one that is always expressed in the phenotype when present. This means that if an individual possesses at least one copy of the dominant allele, the traits associated with that allele will be observable in their physical appearance or biochemical characteristics. Dominant alleles mask the effects of recessive alleles when they are paired together, leading to the phenotype being determined by the dominant one.

For instance, in a genetic cross, if one allele is dominant and the other is recessive, any offspring that inherit the dominant allele will exhibit the associated dominant trait, regardless of whether they inherit the recessive allele alongside it. This is a fundamental concept in Mendelian genetics, which helps explain how traits are passed from one generation to the next. Understanding this concept is crucial for studying inheritance patterns and genetic variations in organisms.