A baby's sex is determined at conception by the combination of sex chromosomes contributed by the sperm and the egg.
The Role of Sex Chromosomes
Human cells typically have 23 pairs of chromosomes, one set inherited from each parent. One of these pairs is the sex chromosomes, which determine biological sex.
- Eggs: An egg cell always carries an X chromosome.
- Sperm: A sperm cell can carry either an X or a Y chromosome.
Fertilization and Sex Determination
The sex of the baby is determined by which sperm fertilizes the egg:
- XX combination: If a sperm carrying an X chromosome fertilizes the egg (which also carries an X chromosome), the resulting embryo will have an XX chromosome pairing, and the baby will typically develop as a female.
- XY combination: If a sperm carrying a Y chromosome fertilizes the egg (which carries an X chromosome), the resulting embryo will have an XY chromosome pairing, and the baby will typically develop as a male.
Therefore, the sperm ultimately determines the sex of the baby. It's a 50/50 chance each time conception occurs.
