In humans XXY individual produced through non-disjunction is sterile male. However, in Drosophila (fruit-flies), XXY set of chromosomes produces a fertile female.This happens because sex determination in Drosophila depends on the number of:
Correct answer: A. X chromosomes relative to the number of autosomes
- A. X chromosomes relative to the number of autosomes
- B. Y chromosomes relative to the number of autosomes
- C. Autosomes relative to the number of XY chromosomes
- D. Y chromosomes relative to the number of X chromosomes.
Explanation
In Drosophila, sex determination is based on the ratio of X chromosomes to sets of autosomes (A), rather than the presence of a Y chromosome, which is crucial in humans. A ratio of 1.0 (for instance, XX:2A) results in a female, while a ratio of 0.5 (for instance, XY:2A) results in a male. Thus, an XXY individual in Drosophila, with a ratio of 1.0, develops as a fertile female. This is different from humans, where the presence of a Y chromosome typically leads to male characteristics. Therefore, the correct answer is related to the number of X chromosomes relative to autosomes, not Y chromosomes.
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About X-linked Recessive Inheritance
X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.
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