1. Molecular Clocks and Evolution Bio 135 Summer 2009

2. mtDNA and Mutations Not subject to recombination or crossover Maternal in Origin- located in the mitochondria Descendant of bacteria- endosymbioant Haploid genome- only one copy of all genes Mutates at Predictable rate 16,569 nucleotides – small, known genome

3. Tree of Life

4. mtDNA:Constant mutation rate due to : 1. MtDNA located in mitochondria 2. Respiration occurs in the mitochondria 3. Respiration produces a known source of potent mutagens called oxygen free radicals 4. H + and OH -: attack bases and phosphate group in DNA

5. Free Radicals and mtDNA Electron “leak” from the electron transport chain during respiration Electrons picked up by Oxygen- O 2 - O 2 - (Free Radical) reacts with DNA to produce mutations Causes cellular aging

6. How to “Set” a Molecular Clock When two groups split off from a common ancestor, each accumulates a unique set of random DNA mutations. Provided that mutations accumulate at a constant rate, then the number of mutations is proportional to the length of time that two groups have been separated. This relationship (number of mutations over time) is called the molecular clock - http://www.geneticorigins.org/mito/theory6.html

7. Mitochondria Eve 1987, Alan Wilson- University of California at Berkeley Used mtDNA polymorphisms in the human population to create a human family tree Modern human ancester- 150,000 years ago In Africa: “Mitochondrial Eve” due to maternal origin of mtDNA Human Genographic Project: https://genographic.nationalgeographic.com/genogra phic/index.html