X and Y chromosomes

• there are 23 pairs of chromosomes in every human body cell
• 22 of the 23 pairs of chromosomes in the human body control characteristics
• the 23rd pair of the human genome are labelled XX or XY
• the 23rd pair of chromosomes in a human's genome determine that person's sex
• males have XY chromosomes
• females have XX chromosomes
• XY chromosomes allow for male characteristics to develop
• XX chromosomes allow for female characteristics to develop
• when making sperm, the X and Y chromsomes are drawn apart in the first division in meiosis.
• there is always a 50% chance that each sperm cell gets an X chromosome and a 50% chance it gets a Y chromosome