A woman gives birth to a boy when she is fertilized by a sperm carrying a Y chromosome.
The Role of Chromosomes in Sex Determination
The sex of a baby is determined at the moment of conception. The mother's egg always carries an X chromosome (female). The father's sperm, however, can carry either an X chromosome or a Y chromosome (male).
- X chromosome from mother + X chromosome from father = XX (girl)
- X chromosome from mother + Y chromosome from father = XY (boy)
Therefore, the father's genetic contribution dictates whether the child will be a boy or a girl. The presence of a Y chromosome from the father's sperm is the determining factor in the development of male characteristics.
Further Considerations
While the above explains the biological mechanism, it's important to note that there are rare exceptions:
- Cases exist where individuals are born with variations in their sex chromosomes, leading to conditions such as XXY (Klinefelter syndrome) or XO (Turner syndrome). These conditions affect sexual development but don't negate the fundamental role of the father's sperm in determining sex. See: More Women Than Expected Are Genetically Men - Novo Nordisk This article highlights the existence of individuals with XY chromosomes who live as women, demonstrating that chromosomal sex and gender identity are not always perfectly aligned.
It's crucial to understand that sex determination is a complex biological process, and this explanation simplifies the process for clarity.
