An albino corn snake is crossed with a normal-colored corn snake. the offspring are all normal-colored. when these first- generation progeny snakes are crossed among themselves, they produce 32 normal-colored snakes and 10 albino snakes. a. how do you know that only a single gene is responsible for the color differences between these snakes? b. which of these phenotypes is controlled by the dominant allele? c. a normal-colored female snake is involved in a test-cross. this cross produces 10 normal-colored and 11 albino offspring. what are the genotypes of the parents and the offspring?

a. We can infer that only one gene is responsible for the only two phenotypes of snakes due to the 3: 1 Mendelian ratio. If there were other genes involved, the ratio would be different.

b. The normal-colored

c. To have raised an albino half offspring, these individuals received a recessive gene from both father and mother. And the other half of normal individuals received at least one dominant gene. Since the statement says that the female snake is a normal phenotype, we know that it has a dominant and a recessive gene. The male snake can only be recessive homozygous to generate offspring half and half. If he was heterozygous for the disease, the offspring would have a 3: 1 ratio.

Here you can see the cross and the genotype of each individual:

      A   x  a

a   Aa       aa

a   Aa       aa

the denominator has a very specific role.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."