Cell Biology: Protein Synthesis Lesson 2 – Mutations( Inquiry into Life pg )
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
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
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
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
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
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
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
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
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
Sickle cell anemia….
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”
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