Question

The Smiths have four children, all girls but the fifth child is a boy. Why did this change occur?
a) the law of averages finally catching up
b) the conception classes taken by the parents
c) the father's contribution of a Y chromosome
d) the mother's contribution of a Y chromosome
e) the timing of the fertility cycles

Answer 1

(c) The occurence of four previous female births does NOT increase the chances for a boy the next time.

Answer 2

It is the father's sperm that determines the sex of the child.
two "Xs" will produce a girl and
an "X" and "Y" a boy.
Since the mother can only contribute an "X" chromosome, the sex of the child depends on whether the father contributes a "Y" (boy) or another "X"
(girl).