Question

XX $Drosophila$ is female but XXY human is an abnormal male. It suggests that

• A. Human and $Drosophila$ have different types of sex determinants.
• B. Y chromosome is the sex determining factor.
• C. X chromosome is the sex determining factor.
• D. XXY $Drosophila$ can also be abnormal.

Answer 1

Answer: (B)

Y chromosome is the sex determining factor.

XX $Drosophila$ is female but XXY human is an abnormal male. This clearly indicates that Y chromosome is sex determining factor. Human females carry XX sex chromosomes. The Y-chromosome carries SRY gene which encodes TDF (Testis Determining Factor). The TDF serves as transcription factor that binds to specific DNA sequence to start the process to develop the embryo into male child. Hence, presence of one Y chromosome in a female causes abnormality in them. Option B is correct answer.