(q037) in mammals, individuals with two x chromosomes are female, and individuals with an x and a y chromosome are male. it had long been known that a gene located on the y chromosome was sufficient to induce the gonads to form testes, which is the main male-determining factor in development, and researchers sought the product of this gene, the so-called testes-determining factor (tdf). for several years, the tdf was incorrectly thought to be a zinc finger protein encoded by a gene called boy. which of the following observations would most strongly suggest that boy might not be the tdf?