Sexual reproduction causes variation
Gametes contain only 23 chromosomes.They contain 1 of each chromosome type but the way they get split up is random.
Chromosomes swap pieces of DNA with each other when they pair u during cell division. This increases variation.
Every egg and sperm is genentically unique.
The joining of an egg with one of millions of sperm is random.
Women - XX
Men - XY
The ratio of baby girls to baby…