Achondroplasia (dwarfism) is an autosomal dominant trait. A man and a woman of normal height have a son with achondroplasia. They want to have another child and wonder what the risk is that he/she will also have this form of dwarfism. The risk is:

The risk is the same as for any other child in the population

Explanation:

In the first instance, the reason for the man and the woman to give birth to a dwarf child is simply as a result of the trait they possess.

Though, the man and the woman are of normal height , but genetically they possess the trait of dwarfism , which is understandably known to be a recessive trait in both of them.

Now, they were able to give birth to a dwarf child because they both donated the recessive trait of achondroplasia.

In this case, the risk will be the same for any child they are intending to give birth too, because the recessive trait of dwarfism might also be donated by the man and the woman.

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