Prevalence of methicillin-resistant Staphylococci species isolated ... by Boa, Tyler T.; Rahube, Teddie O.; Fremaux, Bastien; Levett, Paul N.; Yost, Christopher K. / Journal of Environmental Health.
The X and Y chromosomes, also known as the sex chromosomes, determine the biological sex of an individual: females inherit an X chromosome from the father for a XX genotype, while males inherit a Y chromosome from the father for a XY genotype (mothers only pass on X chromosomes).
A baby's sex is determined at fertilisation. A chromosome from the father's sperm determines whether the child is male or female. If an X chromosome is present the baby is a girl; if a Y chromosome is carried by the sperm instead, the baby is a boy.