Genes A and B are located on the same chromosome.Two parent organisms with the genotypes AABB and aabb were crossed.One of the resulting AaBb offspring was experimentally crossed with an aabb individual.The final offspring genotypes were AaBb,aabb,Aabb,and aaBb. Which of the final offspring genotypes were produced through crossing-over?

Question

Quizplus · Accepted Answer

The only possible way to get the Aabb and aaBb genotypes is through crossing-over. This is because in the original parents, the A and B alleles were present on the same chromosome, and the a and b alleles were present on the other chromosome. During meiosis in the AaBb offspring, crossing-over could have occurred between the A and a alleles, and/or between the B and b alleles, leading to the production of gametes with the genotypes Ab and aB. If these gametes fused with the gametes from the aabb parent, the resulting offspring would be Aabb and aaBb, respectively. The other two genotypes, AaBb and aabb, could have been produced either through segregation of alleles or crossing-over.

Genes a and B Are Located on the Same Chromosome