Question

In any mating between humans, what are the chances that a boy will born? What about the chances for a girl?

Answer 1

The sex of an embryo is purely determined by the chromosome which it acquires from the male parent.

Explanation:

In females, sex chromosomes are XX and in males the sex chromosomes are XY. If the embryo gets X chromosome from female parent and X chromosome from male parent then the result will be XX which is a girl.
If the embryo gets X chromosome from female parent and Y chromosome from male parent then the resultant will be XY which is a boy.