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 therefore many 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