Genes are very small structures inside almost every cell of the body.
Genes are the instructions, or blueprints, that tell our body how to grow and develop, build necessary proteins, and thus determine an individual's characteristics, such as eye color and blood type. It is estimated that there are about 100,000 genes, each of which is an instruction that the cells of the body need to grow and survive. Genes come in pairs and are made of strands of genetic material called deoxyribonucleic acid , or DNA . They line up similar to beads on a string to form larger structures called chromosomes . Genetic disorders are caused when the instruction coded by a particular gene is changed and the gene can no longer perform its proper function.