In Drosophila the XXY condition leads to femaleness whereas in human beings the same condition leads to Klinefelter's syndrome in male. It proves:
- Y chromosome is active in sex determination in both human beings and Drosophila
- In Drosophila Y-chromosome decides femaleness
- Y chromosome of man have genes for syndrome
- In human beings Y chromosome is active in sex determination
Answer
(4) In human beings Y chromosome is active in sex determination
Solution
In Drosophila sex depends on the ratio of X chromosomes to autosome sets; an XXY fly is a female, so the Y chromosome plays no role in deciding sex.
In human beings an XXY individual (Klinefelter's syndrome) is a male in spite of two X chromosomes ⇒ the presence of Y alone decides maleness (the Y carries the testis-determining gene).
∴ In human beings the Y chromosome is active in sex determination.
Answer: (4)