1. Mutations Changes in DNA may result in disease

2. Mutations: Page 96 1) Define mutation from page 224 in your textbook. 2) Decide from paragraph 2 if all mutations are bad. Write down on your left side page what you determine 3) If there is a mutation, what can happen to a protein?

3. Point Mutations: 3 Types Substition, Insertion, or deletion of a nucleotide.

4. Point Mutations: Substitution One N-base is substituted for another. The change in DNA results in a different mRNA codon. The different codon may result in a different amino acid. A change in the amino acid sequence of a protein will likely change the protein’s shape. (Remember-shape determines function!)

5. Point Base Mutation: From the Insulin Lab Section #3 The first 9 DNA bases where: TACAAACAT Find the mRNA, then find the 3 amino acids Now replace the first letter with another base. Record what happens to the amino acids.

6. An Example of Substitution: Sickle cell anemia A disease resulting from an incorrect amino acid in the hemoglobin protein (the protein in red blood cells that carries oxygen). The protein has the wrong shape, so the blood cells become “sickled”, causing numerous physiological problems.

7. Another Type: Frame-shift mutations Results from either: A. Insertion A N-base is inserted B. or deletion A N-base is deleted. Shifts the “reading-frame” of mRNA codons. All codons “downstream” are affected. Causes many amino acids to be incorrect in the protein.

8. Write out the same DNA sequence : TACAAACAT 1 st : Insert one extra base at the beginning, what happens? Write down the resulting amino acids 2 nd : Take out 3 bases from the beginning, what happens? Write down the resulting amino acids

9. What can point mutations cause? Sequence of the amino acid changes Number of the amino acid changes Type of amino acid changes What does this cause to happen in the protein?

10. Genetic disease and frameshift mutations Cystic fibrosis: deletion of 3 bases results in a protein that is missing one amino acid. Muscular dystrophy: caused by insertions/deletions in a critical muscle protein.

11. Cancer is a disease that results from mutations All types of cancer have one thing in common; control of the cell cycle is defective. Cell division goes “out of control” resulting in tumors. The cell cycle is regulated by proteins. If these proteins are defective, cells divide prolifically.

12. Developing cancer is a multi-step process It takes more than a single mutation for cancer to develop. This helps explain a few things:  Older people are more likely to get cancer. The longer someone lives, the more mutations accumulate in their DNA.  Some people have a predisposition to get certain types of cancer, such as breast cancer. If someone inherits a mutation they need only get one or two more to develop cancer.

13. Causes of mutations Errors in DNA replication.  DNA polymerase “proofreads” during replication and catches most errors. X-rays, UV light, and other types of radiation.  Sunscreen helps prevent melanoma, skin cancer. Toxic chemicals  Smokers are more likely to get lung and mouth cancers, etc.