Please consider the following question:

Genes A and B are located on the same chromosome. If two individuals with the genotype shown below are crossed, which genotype could be formed? enter image description here Let / represent the line in the image above. a.)AB/ab b.)Ab/Ab c.)aB/aB d.)AB/Ab

Why can't the answer to this question be all of the choices? I thought that recombination was completely randomized through the process of crossing over. Why is only one of the choices correct and how would I go about doing this on my own?

  • $\begingroup$ The answer is for Genes A and B on the same chromosome is a. AB/ab $\endgroup$ – user19978 Nov 13 '15 at 1:33

One of the alleles for each gene must come from the parent on the right hand side. That parent only has a and b alleles (is homozygous) - meiotic crossing over will not change this. So the offspring must inherit at least one a and one b. That should point you to the answer.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.