Final answer:
With hypertrichosis inherited as a dominant allele, there is a 100% chance that at least one parent has the trait and a 50% chance that another sibling would inherit it.
Step-by-step explanation:
A child with hypertrichosis who has the gene inherited as a dominant allele indicates that at least one of the parents must have the gene. Since dominant alleles only require one copy for the trait to express itself, if the child has hypertrichosis, one parent must have passed this allele on. This means that there is a 100% chance that at least one parent has excessive body hair, assuming no new mutations occurred. For another sibling to be born with hypertrichosis, the same logic applies. If we presume one parent is heterozygous (one dominant allele for hypertrichosis, one recessive allele for normal hair), each child has a 50% chance of inheriting the dominant allele for hypertrichosis. The correct answer would be b) 50% and 50%.
If the gene for hypertrichosis is inherited as a dominant allele, the chance that at least one parent has excessive body hair is 50%. This is because if one parent has the dominant allele, they will exhibit the phenotype of excessive body hair.
As for the chance that another sibling would be born with hypertrichosis, it depends on the genotypes of the parents. If both parents are carriers of the dominant allele, there is a 25% chance that another sibling would be born with hypertrichosis. This is because there is a 50% chance that each parent will pass on the dominant allele to the child, resulting in a 25% probability for the child to be homozygous dominant (affected).