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ChapTer 20: Human Evolution

ChapTer 20: Human Evolution. Understanding “Mitochondrial Eve” and the Out of Africa hypothesis. Learning goals. To understand early human evolution. The “out of Africa” theory and the evidence that supports it.

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ChapTer 20: Human Evolution

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  1. ChapTer 20: Human Evolution Understanding “Mitochondrial Eve” and the Out of Africa hypothesis

  2. Learning goals • To understand early human evolution. The “out of Africa” theory and the evidence that supports it. • To understand how mitochondrial DNA analysis has provided evidence to support the “out of Africa” theory of human evolution. Required reading: Chapter 20: human evolution

  3. Learning objectives • Understand the differences between mitochondrial DNA and nuclear DNA. • Understand how mitochondrial DNA is inherited • Understand the methodology of mitochondrial DNA analysis and how it is used to trace ancestry. • Discuss complementary ancestry-tracing methods (e.g. Y-chromosome analysis) • Understand how data obtained from mitochondrial DNA analysis has provided support for the “out of Africa theory” of human evolution

  4. Nuclear DNA vs Mitochondrial DNA • Nuclear DNA undergoes homologous recombination • Maternal and Paternal DNA are mixed • Mitochondrial DNA does NOT undergo recombination Maternal chromosome Paternal chromosome Offspring inherit mixed chromosomes Circular Mitochondrial chromosome

  5. Mothers pass mitochondrial DNAdirectly to offspring Sperm only contributes paternal DNA

  6. Activity:“Mitochondrial Eve” and the inheritance of mtDNA

  7. MtDNA can be used to trace human ancestry through maternal lines

  8. Finding “Mitochondrial Eve” • Wilson et al (1987) collected mtDNA samples from people all over the world • How did they trace these DNA sequences back to a single origin?

  9. Find the most likely ancestral sequence • Imagine you found the following DNA sequences from mitochondria samples from several individuals. Can you reconstruct the likely ancestral sequence? AAGCCGTT AATCCCTA CATCGGTA AAGCCGTA AATCCCAA CATCCGTA Think to yourself and then discuss with your neighbor A A T C C G T A

  10. Through sequence analysis scientists can trace a mitochondria’s history AATCCGTA AAGCCGTA CATCCGTA AATCCCTA CATCGGTA AAGCCGTT AATCCCAA

  11. Ancestry can be traced along paternal line using Y Chromosome analysis

  12. Activity: Think-pair-share • mitochondrial DNA has a high mutation rate relative to nuclear DNA. This quality of mitoDNA is important for tracing ancestry in a relative new species such as modern humans. • Based on this information can you predict the relative amount of mutations in mitochondrial DNA from the following human populations? How can the amount of mutation in mitochondrial DNA be used to support the “out of Africa” theory? • North America • South America • Africa • Australia • Europe • Asia

  13. Early humans originated from one geographical region

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