P-elements are a type of transposon commonly used in Drosophila (fruit fly) rese
ID: 64682 • Letter: P
Question
P-elements are a type of transposon commonly used in Drosophila (fruit fly) research. A common marker for P-elements is the miniwhite + gene, an engineered version of the white locus. Flies mutant for the natural white have white eyes instead of wild-type red eyes. A miniwhite + gene on a P-element in a white mutant will produce eye pigment, and will act as a dominant marker indicating that the P-element is present.
P-elements used for research are nonautonomous, meaning that they do not encode their own transposase. The transposase is supplied using a second locus, where the transposase enzyme is no longer within a transposon and thus is immobilized (meaning that it cannot move itself). For flies with both a nonautonomous P-element and immobilized transposase, the P-element can move within the genome.
A researcher is interested in screening for P-elements inserted into a region on chromosome 3. To produce new insertions, she crosses females homozygous for a miniwhite + P-element on the X chromosome with males homozygous for immobilized transposase on chromosome 2.
The researcher then crosses the F1 males (XP{miniwhite+}/ Y; transposase / +) to female flies that are homozygous for the white mutation. She selects F2 males that have eye pigment present (indicating that they have a P {miniwhite +} insertion somewhere in their genome).
Why does the researcher select these F2 males? Select all statements that are true.
a) In this cross, most F2 males will have eye pigment because they inherit the XP{miniwhite+} chromosome with a P-element that did not move.
b) In this cross, most F2 males will have no eye pigment because they cannot inherit the X chromosome that had the original P {miniwhite +} insertion on it.
c) In this cross, F2 males with eye pigment result from the P-element moving to a new location on an autosome.
d) In this cross, F2 males with eye pigment result from the P-element remaining at its original location on the X chromosome.
a) In this cross, most F2 males will have eye pigment because they inherit the XP{miniwhite+} chromosome with a P-element that did not move.
b) In this cross, most F2 males will have no eye pigment because they cannot inherit the X chromosome that had the original P {miniwhite +} insertion on it.
c) In this cross, F2 males with eye pigment result from the P-element moving to a new location on an autosome.
Explanation / Answer
Answer: c)
The movement of P element (containing miniwhite+ gene) to an autosomal location in the eggs of the mother results in males with eye pigmentation.
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