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.

Human Genome Project  Purpose: to sequence the entire human genome  Completed in 2003  >1,200 genomes sequenced now (1000 bacteria, 80 archaea, & 124 eukaryotic species)

Human Genome Project

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

Transposable Elements  Make up 75% of repetitive DNA  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 transposase  Requires enzyme transposase

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

Genome Evolution  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

Illustrative Example: Antifreeze Gene in Fish  Antifreeze proteins (AFP):  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  Antarctic fish: old protein gene transformed into a new gene with new structure/function  Gene mutates  duplicated  divergent evolution

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

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

Homeotic genes Homeotic genes: master regulatory genes Control placement and spatial organization of body parts Homeobox 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