IMAT 2021 Q30 [Sex Cells]

Practice Question Solving
1

The SRY gene is normally located on the human Y chromosome. This gene initiates the development of male characteristics.

Using this information, which of the following statements about the SRY gene is/are correct?

  1. Insertion of the SRY gene into an X chromosome of a female zygote could give it male characteristics.

  2. A sperm cell arising from incorrect division, which has a functional SRY gene, could give rise to a female with a sex chromosome trisomy following fertilisation with a normal ova.

  3. During meiosis, crossing over could result in the formation of ‘X’ sperm with the SRY gene, which could cause male characteristics after fertilisation.

A 1 and 3 only

B 2 only

C 3 only

D 1 and 2 only

E 1 only

2

my thinking is:
1 - is correct since it’s logical
2 - is not correct since if a sperm has “a functional SRY gene” then it has a Y-chromosome, thus it wouldn’t be called female
3 - is correct since it’s logical too

P.S. I checked and the answer is A, however now I’m questioning “if the 3rd statement is correct and it is possible to have a female with two X-chromosomes where one has a SRY gene, then it is also possible to get a female with trisomy XXX, where one X-chromosome has an SRY gene too(?) Then the 2nd statement should be correct too?”

am I nuts or does it make sense, any thoughts on that will be appreciated

4 Likes