The human body is made up of trillions of cells that provide structure for the body, process the nutrients we receive from food, create energy, and perform many other functions. All the cells in the body contain the same genetic material, DNA.
Genes are made up of DNA, and strands of DNA make up the chromosomes that are found in the nucleus of cells. Each person has 46 chromosomes—23 from the mother, and 23 from the father. The Human Genome Project estimates that humans have about 25,000 genes, and has mapped the location of each gene on each chromosome, enabling researchers to identify genes that are associated with different functions.
The genes we inherit from our parents help to determine who we are physically—from the color of our eyes and hair to our susceptibility to certain diseases, including cancer.