What gene product is most likely for the following case?
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.
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