Which one of the following statements is correct for dosage compensation in human?
1
X-chromosome inactivation in female occurs in a zygote immediately after fertilization.
2
X-chromosome inactivation is non-random, in some individuals maternal X is inactivated while in others paternal X-chromosome is inactivated.
3
Y-chromosome of males is seen as Barr body.
4
The body of female is a mosaic of cells, some having paternal X- and others having maternal X-inactivated.