Final answer:
Most people have five fingers, despite the dominance of the polydactyl allele, because this allele is very rare in the human population. Dominance indicates that traits can be visible in the presence of only one dominant allele, which is significant in the context of autosomal dominant disorders and complex inheritance patterns in human genetics.
Step-by-step explanation:
The question you've asked pertains to why most people have five fingers if the allele for polydactyly (six fingers) is dominant. The answer is that the polydactyl allele is very rare in the human population. While polydactyly is a condition where an individual has extra fingers or toes, it is not commonly seen because having the allele is unusual. Dominance in genetics means that a dominant allele's trait will be visible when a heterozygous pair includes one dominant and one recessive allele. In this case, although the polydactyl trait is dominant, it is not prevalent due to the rarity of the allele carrying it.
Human genetics explores how different alleles are expressed in traits. Autosomal dominant disorders, such as Huntington's disease, showcase how a single copy of a mutant allele can result in the expression of a disorder. However, patterns of inheritance can also show codominance, incomplete dominance, and lethality, indicating that genetics can be much more complex than a simple dominant/recessive relationship.
Medical researchers are focused on understanding these inheritance patterns to predict the likelihood of genetic disorders being passed on to offspring, which underscores the importance of studying and comprehending how various alleles manifest within the human population.