Baby boy or girl? Dad’s genes determine the sex of his children.
A study by Newcastle University can help prospective parents work out the odds for having a boy or girl. Involving 556 387 people from North America and Europe dating back to 1600, researchers found that men inherit a tendency to have more sons or more daughters from their parents.
A man that has many brothers is more likely to have a boy, while a man with many sisters is more likely have a baby girl. When a man’s sperm carries an X chromosome, it combines with the mother’s X chromosome to make a baby girl (XX) and when a man’s sperm carries a Y chromosome it combines with the mother’s X chromosome to make a boy (XY). The study suggests that a yet undiscovered gene controls the number of X or Y chromosomes in a man’s sperm.
To complicate matters, even though the mother does not decide the sex of her own children, she can also pass on the gene to her son that will decide the sex of his children. For this reason it currently limits the ability to work out the odds for having a boy or girl, to the number and sex of dad’s siblings.
