1. Mutation The principal evolutionary mechanism in bacteria. For all organisms: the only source of new genetic information. Mutation: any heritable change in the structure or amount of genetic material. Different levels of mutation DNA: mistakes made during DNA replication Spontaneous (random) Only mutations occurring during meiosis can affect the next generation.

5. Effects of a mutation Depends on how it affects the functioning of the protein. Is a mutation harmful or beneficial? Determined by the environment.

6. Hemoglobin: 2 alpha chains, 2 beta chains Gene for the alpha chain in chromosome 16 Gene for the beta chain in chromosome 11

7. Natural Selection in Humans: Alternative hemoglobins and malaria Hemoglobin A considered normal Hb A /Hb A Hemoglobin S is an alternative form Hb S /Hb S Phenotype: Sickle-cell anemia—destruction of red blood cells. fatal without medical intervention. Hb A /Hb S Phenotype: Sickle cell trait Debilitating only in situations of low oxygen availability

9. Frequency of Hb S allele Frequency of malaria Estimated malarial cases: 2006-2008:243,000,000 Estimated malarial deaths: 2006-2008:863,000

10. Base substitution Hemoglobin molecules stack when O 2 is low Cells deform Beta-chain Affected 146 aa 6 th aa from end of beta chain

11. Heterozygotic individuals (Hb A /Hb S ) do not experience sickle cell anemia. The environment of the rbc with Hb A /Hb S is not conducive to survival of the malaria parasite. Without medical intervention, natural selection operates against two groups: – 1. Hb A /Hb A : individuals die from malaria. – 2. Hb S /Hb S : individuals die from sickle cell anemia. – Hb A /Hb S is favored, therefore can the Hb S allele be eliminated?