Genes contain instructions for all of our traits – eye color, hair color, aspects of our health – many things that make us who we are. Although we can’t see them, genes are in the millions of cells throughout our bodies. Genes are found in structures called chromosomes, which are also in our cells. Genes are made up of chemical building blocks, which is DNA.
When we have kids, we pass our genes down to them through our sperm cells (if we are males) or egg cells (if we are females). Sperm and egg cells contain half of our chromosomes (and half of our genes). Genes from the sperm and the egg combine to form new cells for a baby. In this way, the baby inherits half their genes from each of their parents.
How our genes are passed down to our kids is random. We have two copies of each gene (one from our mom and one from our dad). We can’t control which copy of a gene we pass to our children or inherit from our parents.