In Drosophila, mutation screening usually involves use of a balancer chromosome that includes three elements: a set of overlapping inversions, an easily recognized dominant mutation, and a recessive lethal mutation that prevents balancer homozygotes from surviving. Which one, or combination, of these elements is necessary and sufficient to suppress crossovers?
A)inversions
B)dominants
C)lethal recessive
D)inversions plus dominant
E)lethal plus inversions

Question

Quizplus · Accepted Answer

The overlapping inversions on the balancer chromosome are necessary and sufficient to suppress crossovers. This is because inversions disrupt the pairing and recombination of homologous chromosomes during meiosis, preventing crossing over between the balancer chromosome and the wild-type chromosome. The dominant mutation and recessive lethal mutation on the balancer chromosome are used to easily identify and select for balancer-containing progeny, but they are not directly involved in suppressing crossovers.

In Drosophila, Mutation Screening Usually Involves Use of a Balancer