Achondroplasia is caused by an autosomal dominant allele and individuals who inherit two copies of the allele do not survive to birth. what is jennifer's genotype for the gene involved in achondroplasia? what is bill's genotype for the same gene? jennifer and bill hope to have a child. what is the likelihood that they will give birth to a child with achondroplasia? what is the likelihood that they will give birth to a child without the condition?

If both, Jenifer and Bill are the

carriers (have one allele for the achondroplasia) that theirs genotypes are Aa (A is dominant, a is recessive allele). In this case:

P: Aa  x  Aa

F: AA Aa Aa aa

This means that ¼ (25%) is the possibility for child to have achondroplasia.

Second case is if one of the parents have homozygous recessive genotype aa (not having allele for achondroplasia):

P1: Aa  x aa

F: Aa Aa aa aa

This means that none of the child will inherit both alleles.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.