DNA Mrs. Nell 7 th Life Science

The chromosomes in the nucleus of a cell contain a code in the form of a chemical called deoxyribonucleic acid, or DNA. DNA controls the activities of cells with this coded information. What is DNA?

The Watson and Crick Model In 1953, two scientists, James Watson and Francis Crick made a model of a DNA molecule. The original DNA demonstration model, designed by Watson and Crick. 1953

Structure of DNA Most living organisms have the same sort of genetic material in their cells- DNA. The shape of the DNA molecule resembles a spiral staircase (called a ‘double helix’). It has two intertwining strands (‘handrails’) made of sugar and phosphate molecules with links across the middle. These links, or rungs, are made of four different DNA base pairs. The bases are represented by letters… A= adenine T= thymine G= guanine C= cytosine

Base Pairing The letters on a DNA molecule always come in pairs. A pairs with T, and G pairs with C. Like interlocking pieces of a puzzle, each base pairs only with its correct partner.

DNA Copies Itself