Cell Biology: Protein Synthesis

1. Cell Biology:Protein Synthesis Lesson 2 – Mutations(Inquiry into Life pg. 500-501)

2. Today’s Objectives • Explain how mutations in DNA affect protein synthesis, including: • Give examples of two environmental mutagens that can cause mutations in humans • Use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders

3. Mutations • A mutation can be considered a biological error that produces a change in the organism in some way • Mutations may have no effect, may be harmful, may be fatal, or may even be beneficial • Naturally occurring mutations are a key idea in the Theory of Evolution

4. Types of Mutations • Chromosomal Mutations • Affect a chromosome and thereforemany genes • Example: Down’s syndrome • Gene Mutations • Affect a single gene • Examples: Hemophilia, sickle cell anemia

5. Types of Mutations • Germinal Mutations • An inherited change or mutation of a sex cell (egg or sperm) so all body cells inherit that defective DNA • Germinal mutations can be chromosomal or gene mutations • Somatic Mutation • A mutation after development is underway • Only some cells are affected • Example: birth marks, cancer

6. Causes of Mutation • Can arise spontaneously (due to an unknown cause) or may be caused by an environmental factor • A factor that increases the chance of mutation is called a mutagen

7. Environmental Mutagens • 1) Chemical – food additives • Hallucinogenic drugs (LSD) • Pesticides/fertilizers • Industrial chemicals • 2) Radiation • Non-visible short wavelengths from electromagnetic spectrum • The greater the exposure the greater the risk

8. Environmental Mutagens • Suspected mutagens are tested on bacteria and other organisms such as fruit flies, and then mammals (rats, mice) • If mutations (such as cancer) develop, the government restricts its use • Mutagens that lead to an increased chance of cancer are called carcinogens

9. Types of Defects • Gene mutations – affect single genes • Result from 1 or more nucleotide changes • Example: Normal strand CAT/ATT/TAG • Addition: CAA/TAT/TTA/G • Added an extra A • Deletion: CTA/TTT/AG • Lost the first A • Substitution: CAT/TAT/TAG • The A and T switched

10. Examples of Mutations • Down Syndrome • A chromosomal translocation • Part of chromosome #21 becomes attached to another chromosome (#12, 14, 14, or 22) • Also have 2 normal chromosome #21 • Sickle Cell Anemia • Substitution of a base to produce a different amino acid • Results in abnormal hemoglobin molecules • Prevalent in African Americans (10% carry the trait) • Causes decreased ability for blood to carry oxygen • 2 chromosomes: 1 normal/1 sickle, actually protects against malaria • If both chromosomes are sickle, the condition is fatal

11. Sickle cell anemia….

12. Examples of Mutations • Cancer • A somatic mutation – affects an individuals body cells • Results in uncontrolled growth of abnormal body cells that fail to stay in the organ where they arose • Hemophilia • A germinal mutation (a mutation of the original sex cells) • Passed on to the individual from a previous generation • Impair the body’s ability to control blood clotting • Known as the “royal disease”

13. Homework • Finish the handout given to you last class • Next day we will have an assignment due in class • Next week (probably Tuesday) we will have a DNA replication/Protein Synthesis test