Genomes and Their Evolution Chapter 21 Genomes and Their Evolution

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

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

Human Genome Project

Comparing Genomes of Bacteria, Archaea, & Eukaryotes

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

Video Clip: What are SNPs?

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

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

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

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

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

Transpositions  chromosomal rearrangements

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

HHMI Short Film: The Birth & Death of Genes

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

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

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

Conservation of homeotic genes