A Linkage Study Has Found That There Is a Gene

A linkage study has found that there is a gene for test-taking skill in a particular region on the long arm of chromosome 4.A search of the human genome sequence shows that this chromosomal region contains a gene of unknown function.This gene encodes a protein that has not only a signal sequence but also seven hydrophobic sequences, each about 20 amino acid residues long.The gene product is most likely:

A) A voltage-gated ion channel.
B) A ligand-gated ion channel.
C) A cytoplasmic protein kinase.
D) A hormone receptor that is linked to G proteins.
E) A hormone receptor with a tyrosine-specific protein kinase activity.