Question

What type of gametes can be produced by simple non-disjunction of the sex chromosomes in a human male? Simple non-disjunction means that non-disjunction occurs in meiosis I or meiosis II, but not in both meiosis I and meiosis II. Choose all answers that are correct.

• 22, 0
• 23, XX
• 23, XY
• 24, XX
• 24, YY
• 24, XY
• 25, XXY
• 25, XXX

Answer 1

Answer)

In males, there are 23 pairs of chromosomes with one X chromosome and one Y chromosome.

During normal meiosis in male sex chromosomes and chromatids segregate in the following pattern :

and result in 4 gametes from one germ cell with

1. 23, X

2.23, X

3.23, Y

4.23, Y

B) If nondisjunction of sex chromosomes occurs in meiosis-1 like below :

It results in gametes with the following genotype :

1.24, XY

2.24, XY

C) If nondisjunction of sex chromosomes occurs in meiosis-2 like below :

It results in gametes with the following genotype :

1.24, XX

2.22, 0

3.24, YY

4.22, 0

Conclusion: Simple nondisjunction of sex chromosomes in males results in the following genotypes of sperms-

If nondisjunction occurs in meiosis-1-

1.24, XY

2.24, XY

If nondisjunction occurs in meiosis-2

1.24, XX

2.22, 0

3.24, YY

4.22, 0

From the above points options 1,4,5,6 are correct.