4.2 - MUTATIONS (c) McGraw Hill Ryerson 2007
The White kermode bear TB page 136 Read page 136 of the textbook out loud TB page 136 (c) McGraw Hill Ryerson 2007
Common human mutations Look up “common human mutations” on Google – what did you find out? Heterochromia Down Syndrome Red hair (and freckles) Celiac disease Cleft chin Colour blindness (c) McGraw Hill Ryerson 2007
What is a Mutation? A gene mutation involves a change in the order of bases (A,C,T,G) that make up the gene. There are several types of gene mutation: Deletion (base missing) Addition (extra base added) Substitution (one base substituted for another) Gene mutations may produce proteins that are beneficial or harmful to the organism, or may have no effect at all. Example: a particular mutated gene produces white coat Kermode bears - they occur as only a small percentage of the population (they are normally black in colour). GNU License Photo See pages 136 - 138 (c) McGraw Hill Ryerson 2007
Effects of Mutations Positive Mutations Negative Mutations When a gene mutation benefits the individual with the mutation Example: Some plants have developed resistance to bacterial and fungal infections. Negative Mutations When a gene mutation harms the individual with the mutation Example: Sickle cell genes in affected humans cause blood cells that are abnormally shaped. Neutral Mutation When a gene mutation has no effect on the individual Example: The white Kermode bear See pages 139 - 140 (c) McGraw Hill Ryerson 2007
Mutagens & Mutation Repair Mutagens are substances or factors that cause mutations Environmental mutagens include: Mercury cigarette smoke X-rays UV rays certain viruses Correcting mutations is difficult, but new techniques such as gene therapy offer hope. See pages 141 - 143 (c) McGraw Hill Ryerson 2007
Mutagens & Mutation Repair Gene therapy is complicated and experimental: For a defective gene to be replaced by a normal version of the gene… A virus must be made which can carry the normal gene The virus must be sent into the nuclei of affected cells The replacement gene from the virus must attach to a chromosome of the target cell’s DNA The target cell must read the newly-attached code to make the desired protein, and must make the correct amount of it This therapy is complicated and not always successful. Does Gene Therapy Work? https://www.youtube.com/watch?v=bLI1Gfb0ynw See pages 141 - 143 (c) McGraw Hill Ryerson 2007
To do now Activity 4-2 A (pg. 137) Reading Check on pg. 141 Announcement: Chapter 4 test will be Weds, May 17 (c) McGraw Hill Ryerson 2007
Activity 4-2a (c) McGraw Hill Ryerson 2007