Achondroplasia Is a Form of Dwarfism in Humans

Multiple Choice

Achondroplasia is a form of dwarfism in humans. It is caused by a mutant allele of the fibroblast growth factor receptor gene (FGFR) that produces an overactive protein. Having one copy of the mutant allele results in dwarfism. Two copies of the mutant allele results in death before birth.
-Based in this information, what can you infer about the inheritance of the FGFR alleles?

A) The mutant FGFR allele is pleiotropic.
B) Some achondroplastic dwarfs are heterozygous for the mutant allele and some are homozygous.
C) The wild-type and mutant FGFR alleles are codominant.
D) The mutant FGFR allele shows incomplete penetrance.