1. Genomes and Their Evolution
Chapter 21
Genomes and Their Evolution

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

3. 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

4. Human Genome Project

5. Comparing Genomes of Bacteria, Archaea, & Eukaryotes

6. 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

7. Video Clip: What are SNPs?

8. 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

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

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

11. Genome Evolution 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

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

13. Transpositions  chromosomal rearrangements

14. 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

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

16. 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

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

18. 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

19. Conservation of homeotic genes