Have people ever said to you, "It's in your genes?" They were probably talking about a physical characteristic, personality trait, or talent that you share with other members of your family. We know that genes play an important role in shaping how we look and act and even whether we get sick. Now scientists are trying to use that knowledge in exciting new ways, such as preventing and treating health problems.
My substance was not hid from thee, when I was made in secret, and curiously wrought in the lowest parts of the earth.
Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them.(Psalms 139:15-16)
What Is a Gene?
To understand how genes (pronounced: jeens) work, let's review some biology basics. Most living organisms are made up of cells that contain a substance called deoxyribonucleic (pronounced: dee-ahk-see-rye-bow-noo-klee-ik) acid (DNA). DNA is wrapped together to form structures called chromosomes (pronounced:krow-muh-soams).
Most cells in the human body have 23 pairs of chromosomes, making a total of 46. Individual sperm and egg cells, however, have just 23 unpaired chromosomes. You received half of your chromosomes from your mother's egg and the other half from your father's sperm cell. A male child receives an X chromosome from his mother and a Y chromosome from his father; females get an X chromosome from each parent.
So where do genes come in? Genes are sections or segments of DNA that are carried on the chromosomes and determine specific human characteristics, such as height or hair color. Because each parent gives you one chromosome in each pair, you have two of every gene (except for some of the genes on the X and Y chromosomes in boys because boys have only one of each).
Some characteristics come from a single gene, whereas others come from gene combinations. Because every person has from 25,000 to 35,000 different genes, there is an almost endless number of possible combinations!