2. 4.2 Mutations

3.  Gene mutation – a change in the specific order of the A, G, C and T bases that make up a particular gene Types 1. Deletion – one base is missing so everything shifts to the left 2. Addition– one base added so everything shifts to the right 3. Substitution – one base is substituted for another

4. 1. Positive mutations – benefits an individual (e.g. developed resistance to disease) 2. Negative mutations – harmful to an individual (e.g. sickle cell anemia where abnormal red blood cells can’t carry oxygen well and block blood flow or cystic fibrosis where mucous builds up in the lungs) 3. Neutral mutations – does not affect an organism (e.g. the white coat colour of the Spirit Bear)  mutagens – substances or factors that can cause mutations in DNA (cigarette smoke, radiation, UV rays, pollutants and some household chemicals) Correcting Mutations  Gene therapy – researchers replace a mutated gene with a healthy copy; very risky