What is the genetic cause of Gynandromorphs occasionally observed in Drosophila?
Answer and explanation
Correct answer: A. Loss of one X chromosome during early embryonic mitotic cleavage in a female () zygote
- Step 1: A gynandromorph is an organism that contains both male and female body segments (e.g., bilateral gynandromorphs).
- Step 2: In Drosophila, sex is determined by the ratio of X chromosomes to autosomes ( ratio: ).
- Step 3: If an zygote loses one X chromosome during its first mitotic cleavage due to non-disjunction, one daughter cell becomes (female) and the other becomes (male), developing into a half-female, half-male mosaic fly.
Answer
Loss of one X chromosome during early embryonic mitotic cleavage in a female () zygote.
Why not the others: Triploid flies () develop as intersexes or meta-females, not mosaic gynandromorphs; Drosophila has no SRY gene (sex is determined by X:A ratio, not Y); Mitochondrial mutations cause metabolic defects.
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