This lesson is about human chromosomes, which are in pairs.
Fertilisation is when chromosomes from parents come together.
The lesson concentrates on one of the pairs, which carries the genes which decide the sex of a person. Main Lesson Most cells in the human body have chromosomes. There are 23 pairs of chromosomes in each human cell. One from each pair comes from our father and one from each pair from our mother. That makes 46 in each of our cells.