Students should be able to describe the structure of DNA anddefine genome

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1. DNA Structure: DNA, or deoxyribonucleic acid, is a molecule that carries most of the genetic instructions used in the development, functioning, and reproduction of all known living organisms. DNA is made up of two strands that twist around each other to form a double helix structure. Each strand is made up of a sugar-phosphate backbone and nucleotide bases. There are four types of bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). Adenine pairs with thymine, and guanine pairs with cytosine. These base pairs are held together by hydrogen bonds, creating the rungs of the DNA ladder.

2. Genome Definition: A genome is the complete set of genes or genetic material present in a cell or organism. The human genome, for example, is composed of approximately 3 billion base pairs of DNA arranged into 46 chromosomes. Each species has a different genome size. For example, the genome of the bacterium E. coli consists of 4.6 million base pairs. The genome includes both the genes (the coding regions) and the noncoding DNA, as well as the genetic material of the mitochondria.