In Drosophila, Mutation Screening Usually Involves Use of a Balancer

question 3

Multiple Choice

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