To make a baby, a man’s sperm meets and joins with a woman’s egg cell inside her body. Inside the man’s sperm are a set of instructions that tell the baby to be a boy or a girl.
The instructions in the man’s sperm cell can either carry the letter "X" or the letter "Y". If the letter is an "X", it means the baby will be a girl. If the letter is a "Y", the baby will be a boy.Unsupported extension