The sperm that determines a baby will be a boy is the one carrying a Y chromosome.
Understanding Chromosomes and Sex Determination
Human cells typically contain 23 pairs of chromosomes. One pair is known as the sex chromosomes, which determine an individual's biological sex.
- Females have two X chromosomes (XX).
- Males have one X and one Y chromosome (XY).
The Role of Sperm
Sperm cells, unlike other body cells, carry only one sex chromosome, either an X or a Y.
- X-carrying sperm: If an X-carrying sperm fertilizes an egg (which always carries an X chromosome), the result will be a female (XX).
- Y-carrying sperm: As the reference states, "if the sperm which fertilises the egg has a Y chromosome, the zygote will be male (XY)".
Table Summarizing Sex Determination
| Sperm Chromosome | Egg Chromosome | Resulting Zygote | Biological Sex |
|---|---|---|---|
| X | X | XX | Female |
| Y | X | XY | Male |
Therefore, it's the sperm with the Y chromosome that results in a baby boy.
