A male with an autosomal dominate disorder such as Achondroplasia has a child with a woman who does not have Achondroplasia. This child has a __ chance of having the disorder: A 50% B 25% C 100% D 75% E 0%
The correct answer and explanation is:
The correct answer is A) 50%.
Here’s an explanation: Achondroplasia is an autosomal dominant disorder, meaning that only one copy of the mutated gene from either parent is required for the child to inherit the condition. In autosomal dominant inheritance, a person with the disorder has one normal allele (N) and one mutated allele (A). The genotype of an individual with Achondroplasia would therefore be Aa.
When a man with Achondroplasia (genotype Aa) has a child with a woman who does not have Achondroplasia (genotype NN), the possible genetic combinations for their child can be determined by a Punnett square.
The father can pass on either his A allele (mutated gene) or his a allele (normal gene), and the mother can only pass on her N allele (normal gene). The possible genotypes for their child would be:
- AN (child inherits the mutated allele from the father and the normal allele from the mother) – this child will have Achondroplasia.
- aN (child inherits the normal allele from the father and the normal allele from the mother) – this child will not have Achondroplasia.
Therefore, there is a 50% chance that the child will inherit the mutated allele (A) from the father, resulting in Achondroplasia. Conversely, there is a 50% chance that the child will inherit the normal allele (a), meaning they will not have the disorder.
Since the disorder is autosomal dominant, the presence of just one copy of the mutated allele is sufficient for the child to express the trait. So, the child has a 50% chance of inheriting the disorder.