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Genomes & Evolution: Human Genome Project, Transposable Elements, Evo-Devo, Homeotic Genes

This chapter discusses the major goals of the Human Genome Project, the comparison of prokaryotic and eukaryotic genomes, the role of transposable elements and retrotransposons, the relationship between evo-devo and genome evolution, and the function of homeotic genes. It also explores bioinformatics and the use of computers and software in sequencing projects.

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Genomes & Evolution: Human Genome Project, Transposable Elements, Evo-Devo, Homeotic Genes

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  1. Chapter 21 Genomes and Their Evolution

  2. What you need to know: • The major goals of the Human Genome Project • How prokaryoticgenomes compare to eukaryoticgenomes. • The activity and role of transposableelements and retrotransposons. • How evo-devo relates to our understanding of the evolution of genomes. • The role of homeoticgenes and homeoboxes.

  3. Bioinformatics • Use of computers, software, and math models to process and integrate data from sequencing projects

  4. Human Genome Project • Purpose: to sequence the entire human genome • Completed in 2003 • Genomes sequenced thus far*: 58,000 prokaryotes, 2700 eukaryotes, 5300 viruses * Data as of 1/27/16

  5. Human Genome Project

  6. Comparing Genomes of Bacteria, Archaea, & Eukaryotes What surprises you?

  7. Human DNA • 3 billion base pairs • ~20,000 genes • Only 1.5% codes for proteins (or RNA) • MostlyRepetitive DNA: sequences present in multiple copies

  8. Video Clip:What are SNPs?

  9. Transposable Elements • Make up 75% of repetitive DNA • Stretches of DNA that can be moved from one location to another in genome • Discovered by Barbara McClintock – corn breeding experiments • 2 Types: • Transposons • Retrotransposons

  10. Transposons • Moves within genome via DNA intermediate • “cut & paste” or “copy & paste” mechanisms • Requires enzyme transposase

  11. Retrotransposons • Move by means of RNA intermediate • Leaves copy at original site • Involves enzyme reverse transcriptase

  12. “QUIZ”! • Choose Transposon or Retrotransposon for each statement. • ____________________ Uses a DNA intermediate • ____________________ Uses reverse transcriptase • ____________________ Uses a “copy paste” or “cut paste” method Transposon Retrotransposon Transposon

  13. Genome Evolution All of this adds to genetic variation! • Insertion effects of transposons: • Can interrupt or alter gene function • Multiple copies of genes • Duplication genes with related functions • Genes diverge by accumulating mutations • Some become nonfunctional pseudogenes • Eventually, new genes with new functions can occur

  14. Multigene Families • Collections of 2 or more identical or very similar genes • Eg. hemoglobin: -globin and -globin gene families

  15. Thoughts on the Human & Mouse chromosomes? Thoughts on the Human & Chimpanzee chromosomes? Transpositions  chromosomal rearrangements

  16. Transposable elements contribute to evolution • Promote recombination, disrupt genes or control elements, & carry genes to new locations • May be harmful or lethal, but can also have small beneficial effects • Provides raw material for natural selection

  17. HHMI Short Film:The Birth & Death of Genes

  18. Illustrative Example: Antifreeze Gene in Fish • Antifreeze proteins (AFP): produced by vertebrates, plants, fungi, bacteria to aid survival in sub-zero environments • Function: bind to ice crystals and prevent growth • Antarctic fish: old protein gene transformed into a new gene with new structure/function • Gene mutates  duplicated  divergent evolution

  19. Evolutionary Development(Evo-devo) • Compares developmental processes to understand how changes can lead to evolution of organisms

  20. Homeotic genes: master regulatory genes • Control placement and spatial organization of body parts Homeobox: widely conserved 180-nucleotide sequence within homeotic (Hox) genes • Found in many groups (fungi, animals, plants) • Hints at relatedness between all life forms

  21. Conservation of homeotic genes

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