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Genomes and Their Evolution

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1 Genomes and Their Evolution
Chapter 21 Genomes and Their Evolution

2 What you need to know: The major goals of the Human Genome Project
How prokaryotic genomes compare to eukaryotic genomes. The activity and role of transposable elements and retrotransposons. How evo-devo relates to our understanding of the evolution of genomes. The role of homeotic genes 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) Mostly Repetitive 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 Choose Transposon or Retrotransposon for each statement.
“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 All of this adds to genetic variation!
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 Transpositions  chromosomal rearrangements
Thoughts on the Human & Mouse chromosomes? Transpositions  chromosomal rearrangements Thoughts on the Human & Chimpanzee chromosomes?

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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