1. Mutations The ultimate source of new alleles

2. Changes to the DNA Sequence Entire set of DNA is copied each time a cell divides. Copying process may not be error free. Chance that a base or series of bases is either copied incorrectly, deleted, reversed or inserted as an addition. Low normal error rate – about one mistake per billion base pairs copied.

3. Think about this error rate! Approx. 3 billion base pairs in human genome (meaning, 3 billion base pairs in each somatic cell) Keeping this error rate in mind, how many errors should you expect each time one of your cells divides? (10 16 cell divisions in a lifetime!!!) How many mutations should you expect in a lifetime? In a day?

4. Mutation as source of genetic variation A large percentage of DNA codes for nothing! Mutations in these sections do not lead to variation. Generally, mutations are kept in check by the DNA repair system. Mutated cells are often either fixed or destroyed! Mutations in somatic cells are not carried forward to the next generations. Only mutations in sex cells can be passed down from parent to offspring and further on.

5. Harmful mutations Most mutations in genes (parts of DNA that code for proteins) are harmful. Usually stop or alter production of a protein. This causes the protein to malfunction. E.g. albinism, thalassemia,

6. Silent mutations Cause no changes in amino acid sequence or final protein product. This may be because: - mutation occurs outside gene region - codon change was for the same amino acid - minor change in amino acid sequence may not have altered the shape or active site of the protein.

7. Beneficial Mutations Sometimes mutations improve the survival chances of organism. Most common example is of flu virus – frequent mutations leading to changes in its glycoprotein “coat” (outer covering) helps it avoid detection by the host’s immune system. MRSA – hospital super bug! Mutations passed down through gametes, if beneficial, continue to persist in a population.

8. Mutagens – agents that speed up the normal rate of mutation Radiation – nuclear, UV, X-rays Diet, Alcohol, Tobacco smoke – diets high in saturated fat, MSG, high alcohol intake, tobacco tar – irritants that induce cancer causing mutations Chemicals – asbestos, alcohol-based solvents like paint thinners and formaldehyde, and many many others… Microorganisms – HIV, HPV, Hepatitis B virus, aflatoxin produced by a fungus commonly growing on peanuts.