what are genes?

A gene is the basic physical and functional unit of heredity. It is a section of DNA made up of a sequence of As, Cs, Ts, and Gs. Genes carry the information that determines physical traits, such as hair and eye color, and other characteristics that are passed on from parents to offspring. Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people, and these small differences contribute to each persons unique physical features. Genes can be broken down into two categories: the Mendelian gene and the molecular gene. The Mendelian gene is a basic unit of heredity, while the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. Genes in general direct specific processes in the body by coding for proteins, and a gene's primary function can be broken down into four general categories: encoding proteins to build something in the body, encoding proteins that help direct the body to do something, encoding RNA that helps regulate gene expression, and encoding RNA that is used directly by the cell.