1. Chapter 11 DNA and GENES

2. DNA: The Molecule of Heredity DNA, the genetic material of organisms, is composed of four kinds nucleotides. A DNA molecule consist of two strands of nucleotides with sugar and phosphates on the outside and bases paired by hydrogen bonding on the inside. The paired strands form a twisted-Zipper shape called a double helix.

3. From DNA to Protein Because adenine can pair only with thymine, and guanine can pair only with cytosine, DNA can replicate itself with great accuracy. This process keeps the genetic information constant through cell division and during reproduction. Genes are small sections of DNA. Most sequences of three bases in the DNA of gene code for a single amino acid in a protein.

4. Genetic Changes The order of nucleotides in DNA determines the order if the nucleotides in messenger RNA in a process called transcription. Translation is a process through which the order of bases in a messenger RNA codes for the order of amino acids in a protein. A mutation is a change in the base sequence of DNA. Mutations may affect only one gene, or they may affect whole chromosomes. Mutations in a egg or sperm affect future generation by producing offspring with new characteristics.