What is a gene?
Genes are sequences of DNA, inherited blueprints for the thousands of proteins that form the building blocks of all life, from bacteria to humans. Proteins make enzymes, which carry out all the bodily processes, like digestion of food, that keep us alive. Quote by Dr Michael Antoniou, a molecular biologist who specializes in the clinical applications of genetic engineering: “Genes are arranged along the DNA in groups or ‘families’. The function of a given gene in a group is dependent on all the other genes that are present within the same family. Furthermore, the genetic activity in one family of genes can affect the function of genes in other groups of genes. It is also clear that genes and the proteins that they give rise to, have co-evolved together to form an extremely intricate, interconnected network of finely balanced functions, the complexities of which we are only just beginning to understand and appreciate.
Each gene has a special job to do. It carries blueprints — the instructions — for making proteins (say: pro-teens) in the cell. Proteins are the building blocks for everything in your body. Bones and teeth, hair and earlobes, muscles and blood, all are made up of proteins (as well as other stuff). Those proteins help our bodies grow, work properly, and stay healthy. Scientists today estimate that each gene in the body may make as many as 10 different proteins. That’s over 300,000 proteins! Like chromosomes, genes come in pairs. Each of your biological parents has two copies of each of their genes, and each parent passes along just one copy to make up the genes you have. Genes that are passed on to you determine many of your traits, such as your hair color and skin color. Maybe Nancy’s mother has one gene for brown hair and one for red hair, and she passed the red hair gene on to Nancy. If her father has two genes for red hair, that could explain her red hair.
A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 30,000 and 40,000 genes. 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. Alleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each person’s unique physical features. The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases.
