An underage patient has signs of achondroplasia (dwarfism). It is known that this is a monogenic disease and the gene that is responsible for the development of such abnormalities is a dominant one. The development of that child's brother is normal. Specify the genotype of the healthy child:

Question

Answer options

AABB
Aa
aa
AA
AaBb

Correct answer

aa

Explanation

Achondroplasia is an autosomal dominant disorder, therefore a normal child from parents with achondroplasia will have to get the good recessive gene from both (aa).

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