Mutations & Evolution

Fig. 14-1

Point Mutations

Frameshift Mutations

Tautomeric Shifts

Fig. 14-2

Fig. 14-3

Deamination

Fig. 14-4

Alkylation

Fig. 14-6

Fig. 14-7

Thymine Dimer

Fig. 14-8

Fig. 14-9

Proofreading by DNA Polymerase

Postreplication Repair

Fig. 14-10

Fig. 14-11

Fig. 14-12

Fig. 14-13

Homologous RecombinationRepair

Fig. 14-15

Mutation as an Agent of Evolution

• Survival of the Fittest = Strongest Survive???????

• Mutations may weaken an individual, but make it more likely to survive in a particular environment.• Example: mutations in the ribosome often cause slower

growth (a sign of “sickness”), but allow the cell to resist macrolide antibiotics.

Some Human Mutations

• Sickle Cell Anemia – mutation in hemoglobin gene.• Increased resistance to malaria.

• Cystic Fibrosis – mutation in a chloride ion channel gene.• Increased resistance to cholera?

• Tay-Sachs Disease – mutation in a lysosomal gene.• Increased resistance to tuberculosis?

Darwin’s Theory of Natural Selection

• Nature “selects” certain individuals among a diverse population to survive.• An organism’s environment is constantly changing, i.e.

newly introduced antibiotics.• Unpredictable!

Genetic Diversity

• One of the keys to natural selection is the existence of a diverse population.• Increases the chance that some individual(s) will survive in the

new environment.