Fun with Science Club®


			Girls and boys are genetically different by only one letter. Beth Tyler 05.03.01 Girls and boys are genetically different by only one letter. Our genes carry much of the information needed to make our bodies grow and function. Genes are found on chromosomes and all of this essential machinery is packaged into the nucleus of our cells. Because cells are very small, people can only see them with powerful microscopes. It wasn't until 1900 that scientists could actually look at these chromosomes. They discovered that humans get 2 sets of 23 chromosomes, one set from each parent, for a total of 46 chromosomes. One of the sets is different in girls and boys, and it is this difference that contributes the most to girls being girls and boys being boys. Here's how it works. All people start out from just two cells, one given by their mother and one given by their father. The egg cell from the mother has 23 chromosomes, including one called the X chromosome. The sperm cell from the father also has 23 chromosomes, including either an X chromosome or a Y chromosome. A baby with an X from the father develops as a girl. A baby with a Y from the father develops as a boy. Many of the physical differences we see between girls and boys and men and women are influenced by genes in this set of chromosomes.


			Atherly, Alan G., Jack R. Girton, and John F. McDonald. 1999. The Science of Genetics, Sauders College Publishing, pg. 46-47.