Final answer:
Polydactyly is a condition characterized by extra fingers or toes, due to a rare dominant allele. Hox gene mutations can cause abnormal body structures and Down syndrome is a type of aneuploidy, the presence of an extra chromosome.
Step-by-step explanation:
A) Polydactyly A condition characterized by extra fingers or toes is called Polydactyly. If the allele encoding polydactyly is dominant, the reason why most people have five fingers instead is because the polydactyl allele is very rare in the human population. Moreover, the appearance of this trait in specific populations, like the Amish, where there's a higher frequency of polydactyly, is an example of a founder effect, where genetic traits of an initial colonist have a marked influence on the genetic variation in a population.Anomalies like these are generally the result of genetic variations and mutations. For example, mutations in Hox genes, which are a group of related genes that control the body plan of an embryo, could lead to various phenotypic effects.
A mutation in a Hox gene is more likely to cause abnormal body length or height or even an altered number of appendages. Disorders related to extra chromosomes, such as Down syndrome, are also genetic conditions where there is an extra copy of chromosome 21, leading to a total of 47 chromosomes rather than the usual 46. This condition is known as Trisomy 21 and is one type of aneuploidy.