Final answer:
Facial dimples may be a dominant trait, but their prevalence in the population depends on allele frequencies and inheritance patterns. Dominance does not guarantee a trait will be more common, as this is influenced by genetic factors such as allele frequency, polygenic inheritance, and incomplete dominance or codominance.
Step-by-step explanation:
If facial dimples are a dominant genotype, one would initially assume that more people would have them. However, dominance in genetics does not necessarily predict prevalence in a population. The presence of a dominant trait like facial dimples depends on various factors, including the gene's allele frequency within the population and whether individuals with the trait reproduce and pass it on more than those without it.
Consider the analogy of a cleft chin as a dominant trait. If a person with a cleft chin who is homozygous dominant (BB) mates with a person with a smooth chin (recessive allele, bb), their children will definitely have a cleft chin. On the other hand, if the cleft-chinned individual is heterozygous (Bb), the offspring will have a 50% chance of inheriting the cleft chin and a 50% chance of having a smooth chin. The phenotype displayed will be a result of the specific combination of alleles inherited from each parent.
The expression of traits can also be influenced by polygenic inheritance, where multiple genes contribute to a particular trait, resulting in a wide range of phenotypical expressions. Moreover, traits that are thought to be purely dominant or recessive may sometimes exhibit incomplete dominance or codominance, leading to a blending of traits.
Adding complexity, recessive alleles may be more common than dominant alleles in certain populations. This frequency, influenced by factors such as genetic drift, mutation, selection, and gene flow, will ultimately impact the prevalence of the dominant phenotype in a population.