Question

A boy is detected to have XYY syndrome, ie has an extra copy of the Y chromosome. Non-disjunction in which parent, and during which meiotic division would lead to this condition?

a) Non-disjunction in the mother during meiosis 1

b) Non-disjunction in the mother during meiosis 2

c) Non-disjunction in the father during meiosis 1

d) Non-disjunction in the father during meiosis 2

Answer 1

Here the boy is detected to have XYY syndrome, ie has an extra copy of the Y chromosome- 47, XYY karyotype.

* Also called jacob's Syndrome.

Y chromosome is passed to offsprings only from male parent in humans. XX is the normal genotype of mother parent and XY is the normal genotype of male parent. So boy can get the Y chromosome only from his father.

Non disjunction occured during Anaphase II stage of Meiosis II created this extra copy of Y chromosome in the sperm.

So this condition is caused by Non disjunction in father in Meiosis 2

Option d is the answer.

NON DISJUNCTION IN THE FATHER DURING MEIOSIS 2 is the answer.