1. 4.2 - MUTATIONS
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2. The White kermode bear TB page 136
Read page 136 of the textbook out loud
TB page 136
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3. 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
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4. 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
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5. 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
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6. 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
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7. 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?
See pages
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8. To do now Activity 4-2 A (pg. 137) Reading Check on pg. 141
Announcement: Chapter 4 test will be Weds, May 17
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9. Activity 4-2a
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