Читать книгу Horse Economics - Vera Kurskaya - Страница 15

Genetic information that determines the traits of a living organism is stored in the nucleus of a cell. Using a microscope, it is possible to observe oblong structures in the nucleus during certain time periods in the life cycle of a cell. These structures, called chromosomes, contain deoxyribonucleic acid (DNA), which is the direct carrier of hereditary information. The molecular building blocks of DNA are the four nucleotides known as adenine, thymine, cytosine, and guanine. A DNA molecule has two strands aligned with each other (like the tracks of a train), forming the familiar double helix. Segments of DNA are called genes. They are essentially the ingredients for the recipe to make a living thing and determine the kind of “products” the cell will manufacture and the characteristics they determine—for ­example, eye or hair color.