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# DNA, Proteins, and Synthesis ## DNA Structure * DNA is located in the nucleus of cells and organized into chromosomes. * DNA is a double-stranded helix. * There are four bases: Adenine, Thymine, Cytosine, and Guanine. * Bases have complementary pairs: A with T, and C with G. ## The Genetic Code...

# DNA, Proteins, and Synthesis ## DNA Structure * DNA is located in the nucleus of cells and organized into chromosomes. * DNA is a double-stranded helix. * There are four bases: Adenine, Thymine, Cytosine, and Guanine. * Bases have complementary pairs: A with T, and C with G. ## The Genetic Code * A region of DNA on a chromosome is called a gene. * Each gene codes for a protein. * The information in DNA is called the genetic code. * Each group of three bases in DNA "codes" for one amino acid. * Each protein is made of several amino acids. ## Proteins * A protein is made up of a chain of amino acids. * There are 20 amino acids, and different combinations will make different proteins. * The sequence of amino acids depends on the sequence of DNA. ## mRNA and Protein Synthesis * A complementary code of DNA is carried from the nucleus to the ribosome by messenger RNA (mRNA). * At the ribosome, the mRNA code is used to determine the order of amino acids. * The amino acids are assembled to make a protein. * This means that DNA indirectly codes for the sequence of amino acids in a protein, and thus its structure and function. * The sequence of bases in DNA codes for the sequence of bases in RNA. * The sequence of bases in RNA codes for the sequence of amino acids in the protein. * The sequence of amino acids in the protein determines the protein's shape. * The protein's shape determines its function. ## Sickle-Cell Anemia * The protein hemoglobin is found in red blood cells. * It binds with oxygen. * A change in one amino acid in the hemoglobin protein can lead to sickle-cell anemia. ## Genetic Engineering * Genetic information can be transferred from one organism to another by genetic engineering. * Steps in genetic engineering of insulin: 1. Identify the section of DNA containing the insulin gene from the human chromosome. 2. Extract the insulin gene. 3. Cut a bacterial plasmid with enzymes. 4. Insert the insulin gene into the bacterial plasmid. 5. Insert the plasmid into a bacterial cell. 6. Bacterial cells copy the plasmid. 7. The transformed bacteria produce a small amount of insulin. 8. The transformed bacterial cells multiply, and all of them produce insulin. ## Cellular Respiration * Respiration is the chemical process in cells that releases energy from food. * Glucose is the main source of energy in cells. * During respiration, glucose is broken down by enzymes in a series of biochemical reactions.