Transcript Pppt
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 • Only 1.5% codes for proteins (or RNA) • 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 Requires enzyme transposase Retrotransposons Move by means of RNA intermediate Leaves copy at original site 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): 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 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: master regulatory genes • Control placement and spatial organization of body parts Homeobox: widely conserved 180nucleotide sequence within homeotic (Hox) genes • Found in many groups (fungi, animals, plants) • Hints at relatedness between all life forms Conservation of homeotic genes