MOLECULAR ECOLOGY AND EVOLUTION

1
MOLECULAR ECOLOGY AND EVOLUTION NATURE AND
SIGNIFICANCE OF MUTATIONS IN EVOLUTION
Point mutations Gene duplication Partial
(internal) gene duplication Genomic
reorganization
2
SPLIT GENES
Concepts of partial gene duplication and gene
shuffling become more realizable if genes are
split into modules. Introns and exons,
especially if exons correspond to domains in
proteins
Exon/intron structure of haemoglobin, b-globin
gene
intron 1
intron 2
240 120 500
550 250 base
pairs
Actually, human gt92 130 223
850
gt129
3
THE ORIGIN OF INTRONS
Introns early Small genes fused, and introns are
the remains of intergenic regions (implies
prokaryotes have lost introns) Introns
late Introns are a consequence of insertion of
unrelated DNA elements (transposition,
retroposition etc.) (implies prokaryotes never
had introns)
complex enzymes domains and exons
4
EXON/DOMAIN SHUFFLING
Dehydrogenases Lactate dehydrogenase
(LDH) Malate dehydrogenase (MDH) Alcohol
dehydrogenase ADH) Glyceraldehyde phosphate
dehydrogenase (GAPDH) Glutamate
dehydrogenase Pyruvate dehydrogenase
5
GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE
6
DOMAINS IN DEHYDROGENASES
A1 and A2 - the NAD-binding domain
7
LACTATE DEHYDROGENASE
8
DOMAINS IN THE CLOTTING CASCADE ENZYMES
From Li Graur (2000)
F1, F2 fibronectin type 1 2 modules AP
apple module GA
gamma-carboxy EG EGF modules
KR kringle module
glutamate domain
9
CLOT LYSIS
tPA

• Plasmin
• a serine protease (trypsin like) which
  specifically breaks down fibrin
• formed from plasminogen (86K protein), by action
  of other proteases urokinase (kidney) or tissue
  plasminogen activator (tPA)

From Stryer
10
L1 RETROTRANSPOSITION
ORF 2
Pol II
ORF 1

AAAAAAAA
6-7 kbp 60,000 copies in human genome, of which
100 can transpose
11
A model showing how L1 retrotransposition can
generate genomic diversity
12
REPETITIVE ELEMENTS
Repetitive elements in the human genome - Li et
al. (2001) SINES 12.5
(Alu 10.7) LINES 18.9
(L1 15.4) DNA transposons 2.7 LTR
elements 7.9 Other
0.1
42.1 Including duplicative transposons?
SINE short interspersed repetitive
element LINE long interspersed repetitive
element LTR long terminal repeat
13
PROCESSED PSEUDOGENES
DNA mRNA precursor mRNA
Reverse transcriptase
DNA
e.g. Mouse alpha globin Human cytochrome c Rat
insulin
14
HORIZONTAL GENE TRANSFER
15
DNA CONTENT OF VARIOUS HAPLOID GENOMES
16
From Pollard Holland (2000)