1. BC Science 9: p. 136-147

2. Gene Mutation  A gene mutation involves a change in the order of the bases (A, C, G, T) that make up the gene.  There are three types of gene mutations: Deletion (base missing) ○ AGTCTGC  AGCTGC Addition (extra base added) ○ AGTCTGC  AGTCGTGC Substitution (one base is substituted for another) ○ AGTCTGC  AGGCTGC

3. The Effect of a Gene Mutation  Gene mutations may cause an organism to produce proteins that are beneficial or harmful to it, or may have no effect at all.  The effect of the gene mutation can be positive, negative, or neutral.

4. Positive Gene Mutations  When a gene mutation benefits the individual. Eg. Some plants have developed resistance to bacterial and fungal infections. These plants are able to produce proteins that protect them.

5. Negative Gene Mutations  When a gene mutation harms the individual. Eg. Red blood cells are unable to create the protein hemoglobin and take on a different shape. These abnormally shaped cells cannot carry oxygen efficiently and cause sickle cell anemia and organ damage.

6. Neutral Gene Mutations  When a gene mutation has no effect on the individual.  The most common of the three types. Eg. A mutation in the DNA of the white Kermode bear causes its fur to be white instead of black. Studies have shown that the fur colour has no effect on the bear’s survival.

7. Mutagens  Substances or factors that cause mutations in DNA are known as mutagens. Eg. Cigarette smoke, radiation from UV rays or X-rays, pollutants such as mercury or cadmium, certain viruses, or household chemicals.

8. Mutagens  Mutagens change the sequence of bases and cause the DNA to become damaged.  The damaged DNA can disrupt the instructions stored in genes and inhibit the correct proteins from being produced.

9. Correcting Mutations  Correcting mutations is difficult, but new techniques such as gene therapy offer hope.  Gene therapy is complicated, expensive and experimental.

10. Gene Therapy 1. A virus is engineered to carry a normal gene. 2. The virus must target the cells with the defective gene. 3. The normal gene must replace the defective gene. 4. The normal gene must then be “switched on” so that the replaced gene produces the proper healthy protein.