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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