Question

The null mutation w- at the w gene results in white-eyed flies. researchers want to map the w gene. the mutant phenotype, however, is very unstable: spontaneous reversals to the wild type are extremely common when rearing mutant flies. what is the likely cause?

a. an insertion interrupts pigmentation gene function in mutant flies
b. the slow accumulation of point mutations at w restore wild type gene function (pigmentation)
c. a transposon is moving around
d. A&C
e. B&C

Answer 1

The spontaneous reversals to wild type in white-eyed flies are likely due to a transposon that moves in and out of the w gene, disrupting or restoring the gene's function that leads to pigmentation.

Step-by-step explanation:

The likely cause for the unstable mutant phenotype where spontaneous reversals to the wild type are extremely common when rearing mutant flies is most likely due to a transposon moving around. Transposons are DNA sequences that can change their position within the genome, sometimes causing or reversing mutations when they insert or excise from a functional gene. This process can disrupt gene function or restore it if the transposon moves out of a previously disrupted gene.

In this case, if the null mutation w- in the w gene results in white-eyed flies and reversals are common, it suggests that the mutation may be due to a transposon inserting in the gene's sequence, which can occasionally excise itself, leading to the restoration of the wild type pigmentation gene function.