What would be the probability of obtaining 6 offspring, 4 of which were dominant and 2 recessive if it was a test cross (Aa x aa) instead of a cross between two heterozygotes? Give your answer to 4 decimal places.

0.0156

Explanation:

If the test cross is between one heterozygous (Aa) and one homologous recessive gene (aa). The possible genotype for their offspring will be

Aa aa Aa aa

The probability of dominant gene (Aa) is 2/4

The probability of recessive gene (aa) is 2/4

The probability that in six offspring 4 is dominant and two recessive is

= 2/4*2/4*2/4*2/4*2/4*2/4

=64/4096

=0.015625

=0.0156 to 4 decimal places

"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."