Evo........

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Evo........
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Evo........Devo
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Evo - Devo Evolution and Development I.
Background
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Evo - Devo I. Background - Embrologists have
long realized that organisms in different phyla
have different developmental "plans"
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Evo - Devo I. Background - Embrologists have
long realized that organisms in different phyla
have different developmental "plans" - And in a
phylum, there is the same developmental plan.
This is not necessarily what we might expect from
random mutation and evolution... why don't we see
as many differences in early developmental traits
as we see in later developing traits?
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- For instance, why do chordates have similar
development, even though cartilaginous fish and
other vertebrates are separated by 400 million
years of divergent evolution?
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Evo - Devo I. Background - Embrologists have
long realized that organisms in different phyla
have different developmental "plans" - And in a
phylum, there is the same developmental plan.
This is not necessarily what we might expect from
random mutation and evolution... why don't we see
as many differences in early developmental traits
as we see in later developing traits? - For
instance, why do chordates have similar
development, even though cartilaginous fish and
other vertebrates are separated by 400 million
years of divergent evolution. - Embryological
development is highly conserved, while
subsequently allowing extraordinary variation....
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED DNA,
RNA, protein synthesis - ALL LIFE
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED DNA,
RNA, protein synthesis - ALL LIFE Membrane
structure and function - ALL EUK's
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED DNA,
RNA, protein synthesis - ALL LIFE Membrane
structure and function - ALL EUK's Cell junctions
- ALL METAZOA
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED DNA,
RNA, protein synthesis - ALL LIFE Membrane
structure and function - ALL EUK's Cell junctions
- ALL METAZOA Hox genes - ALL BILATERIA
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED DNA,
RNA, protein synthesis - ALL LIFE Membrane
structure and function - ALL EUK's Cell junctions
- ALL METAZOA Hox genes - ALL BILATERIA Limb
formation - ALL LAND VERTEBRATES
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED - Many
enzymes are more than 50 similar in AA sequence
in E. coli and H. sapiens, though separated by 2
billion years of divergence. - Of 548 metabolic
enzymes in E. coli, 50 are present in ALL LIFE,
and only 13 are unique to bacteria.
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED - Many
enzymes are more than 50 similar in AA sequence
in E. coli and H. sapiens. - Of 548 metabolic
enzymes in E. coli, 50 are present in ALL LIFE,
and only 13 are unique to bacteria. - So the
variation and diversity of life is NOT due to
changes in metabolic or structural genes... we
are all built out of the same stuff, that works
the same way at a cellular level.
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Evo - Devo I. Background II. Core Processes -
Basic biological processes are CONSERVED, and the
enzymes that perform them are CONSERVED - Many
enzymes are more than 50 similar in AA sequence
in E. coli and H. sapiens. - Of 548 metabolic
enzymes in E. coli, 50 are present in ALL LIFE,
and only 13 are unique to bacteria. - So the
variation and diversity of life is NOT due to
changes in metabolic or structural genes... we
are all built out of the same stuff, that works
the same way at a cellular level. - Variation is
largely due to HOW these processes are
REGULATED... 300 cell types in humans, all
descended from the zygote all genetically the
same.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Development is NOT a
single process
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Development is NOT a
single process - Development is a well
choreographed dance of many parallel processes...
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Development is NOT a
single process - Development is a well
choreographed dance of many parallel
processes... - How is the parallelism
maintained, ESPECIALLY as one process evolves?
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Development is NOT a
single process - Development is a well
choreographed dance of many parallel
processes... - How is the parallelism
maintained, ESPECIALLY as one process evolves? -
Because they may be triggered by the same (or
subsets of the same) REGULATORS... these are
transcription factors that can turn suites of
metabolic/structural genes on and off.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Development is NOT a
single process - Development is a well
choreographed dance of many parallel
processes... - How is the parallelism
maintained, ESPECIALLY as one process evolves? -
Because they may be triggered by the same (or
subsets of the same) REGULATORS... these are
transcription factors that can turn suites of
metabolic/structural genes on and off. And
transcription factors can interact.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Best (and most
fundamental) examples are HOX genes. These are
'homeotic genes' that produce a variety of
transcription factors. The production and
localization of these transcription factors are
CRITICAL in determining the 'compartments' of
bilaterally symmetrical animals.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Duplication of hox
genes can lead to differential regulation in
different segments, and different phenotypes in
different segments.
inhibition of limb development
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Duplication of hox
genes can lead to differential regulation in
different segments, and different phenotypes in
different segments. Each gene produces a DNA
binding protein that turns on a set of genes...
different hox genes produce different binding
proteins, that stimulate different sets of
genes...that are ALL regulated by THIS
transcription factor (linked regulation -
coordinated response).
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Effects can be
profound
antennaepedia
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Effects can be
profound - But they demonstrate the 'modularity'
of the developmental plan - only single units are
affected.
Bithorax
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Effects can be
profound - But they demonstrate the 'modularity'
of the developmental plan - only single units are
affected.
- 'Master Switches' that initiate downstream
cascades that can be very different... like
compound or vertebrate eyes.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - and they are still
integrated with the rest of the organism For
example, the length of a breed's snout correlated
directly with the number of repeats in a gene
called Runx-2. Runx-2's tandem repeat consists of
two different three-base sequences, randomly
ordered along the length of the repeat. If
there's more of one threesome relative to the
other, that breed's muzzle tends to be longer and
straighter. Fonden and Garner. 2004. PNAS
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Types of Regulation
Enhancer - upstream activation sequence. Binding
site for transcription factor. Mutation here is
cis-regulation (within the operational "cistron")
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Types of Regulation
mutation in the transcription factor gene is
called trans-regulation
Enhancer - upstream activation sequence. Binding
site for transcription factor. Mutation here is
cis-regulation (within the operational "cistron")
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - Types of Regulation
mutation in the transcription factor gene is
called trans-regulation
Enhancer - upstream activation sequence. Binding
site for transcription factor. Mutation here is
cis-regulation (within the operational "cistron")
Each type modulates activity about 50 of the
time...
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - NOVELTY
Mutations may make an enhancer available to a
different transcription factor... and now that
gene is 'on' in a new tissue and can be used for
a new function. Crystallins are heat-shock
proteins and mitochondrial enzymes but when they
are expressed in the eye, they are used as
transparent structural proteins in a completely
different process.
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And of course, how they are arranged in lenses
vary.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - NOVELTY
OR, an entirely new binding site can evolve -
they are typically quite short (6-10 bases) so
they will arise frequently by random
mutation...selection can then favor new
regulatory pathways.... KEEP THE OLD, but GAIN
NEW (sound familiar???)
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
ac, The wing spots on male flies of the
Drosophila genus. Drosophila tristis (a) and D.
elegans (b) have wing spots that have arisen
during convergent evolution. Drosophila
gunungcola (c) instead evolved from a spotted
ancestor. d, Males wave their wings to display
the spots during elaborate courtship dances.
(Photographs courtesy of B. Prud'homme and S.
Carroll.)
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
yellow gene
enzyme for pigment production
"spotted wing"
In their previous research, they found that
spotted members of both spotted clades had same
cis regulatory element (CRE). So, they
hypothesized that all members of the clade were
descended from a spotted ancestor (99 chance
ancestor was spotted - fig.)
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
yellow gene
LOSS of the spot within this clade (an example of
convergent evolution AND reversion) occurred by
different mutations in same CRE.
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
yellow gene
LOSS of the spot within this clade (an example of
convergent evolution AND reversion) occurred by
different mutations in same CRE. Importantly,
yellow is still on elsewhere. This is a
pleiotropic gene that has many effects.
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
yellow gene
LOSS of the spot within this clade (an example of
convergent evolution AND reversion) occurred by
different mutations in same CRE. Importantly,
yellow is still on elsewhere. This is a
pleiotropic gene that has many effects. Shutting
it "off" by a mutation in the gene would cripple
it's activity throughout the organism. Here,
through cis regulation, it's expression is
modulated in only one tissue (wing).
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
yellow gene
spotted wing
In D. tristis, the yellow gene is enhanced by a
completely different, independently evolved CRE.
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- Prud'homme et al. 2006. Repeated morphological
evolution through cis-regulatory changes in a
pleiotropic gene Nature 4401050-1053.
Two gains and two losses are due to independent
changes in the regulation of the yellow gene. The
developmental 'scaffold' for forming spots
exists... subsequent evolution of enhancement can
form a new anatomical trait, which can be rapidly
selected for by sexual selection.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation - HETEROCHRONY -
paedomorphism - peramorphism - allometry All
simply changes in the developmental rates of
different structures or processes.
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Allometry in horn length relative to body size in
Beetles
Scarabaeidae Onthophagus
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Evolution of legs from fins
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Evolution of legs from fins
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior

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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors - hypoxia -
stimulates cell to produce endothelial growth
factor
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors - hypoxia -
stimulates cell to produce endothelial growth
factor - neighboring vascular tissue grows
towards the source of growth factor
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors - hypoxia -
stimulates cell to produce endothelial growth
factor - neighboring vascular tissue grows
towards the source of growth factor - and
BINGO... now you have vascular tissue and hypoxia
is corrected
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors - hypoxia -
stimulates cell to produce endothelial growth
factor - neighboring vascular tissue grows
towards the source of growth factor - and
BINGO... now you have vascular tissue and hypoxia
is corrected - Nerves and vessels grow in
response to local signals... the pattern is not
hardwired.
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Evo - Devo I. Background II. Core Processes III.
Weak Linkage Regulation IV. Exploratory Behavior
- environmental cues affect cell activity -
production of growth factors - hypoxia -
stimulates cell to produce endothelial growth
factor - neighboring vascular tissue grows
towards the source of growth factor - and
BINGO... now you have vascular tissue and hypoxia
is corrected - Nerves and vessels grow in
response to local signals... the pattern is not
hardwired. - So, if bone growth changes,
muscles cell growth responds, and correct
ennervation and vascularization occurs on this
new platform.