Final answer:
The likelihood of a patient acquiring Huntington's disease if his father is a carrier and has the illness is 50%. Huntington's disease is an autosomal dominant disorder, and each offspring has a 50% chance of inheriting the disease-carrying allele.
Step-by-step explanation:
Understanding Huntington's Disease Inheritance
Huntington's disease is a condition where the nervous system gradually deteriorates, typically showing symptoms in middle age. It's caused by a dominant allele, meaning that a person only needs one copy of the mutant gene to exhibit the disease. When considering what is the likelihood of a patient acquiring Huntington's disease if his father is a carrier and has the illness, it is important to recognize that Huntington's is not an X-linked disorder, but an autosomal dominant disorder. Therefore, gender does not affect the likelihood of inheriting the disease.
Using a Punnett square to predict the inheritance patterns for Huntington's disease, we understand that if one parent has the disease (Hh), they possess one normal allele (h) and one Huntington's allele (H). The unaffected parent with a normal genotype (hh) can only contribute a normal allele. This results in a 50% chance that any given offspring will inherit the Huntington's allele (H) and therefore the disease.
So, the answer to the question is B. 50%. Each child of a parent with Huntington's disease has a 50% chance of inheriting the disease, regardless of whether the offspring is male or female.