lecture_22_SW_evo_devo_updated

lecture_22_SW_evo_devo_updated - Evo‐Devo:
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Unformatted text preview: Evo‐Devo:
 Understanding
the
Evolu5on
of
Form
 -  ow do novel features appear? h -  ow have genetic changes lead to h morphological evolution? -  ow have complex structures evolved? h Steps
in
Gene5c
Analysis
 1)  mutagenesis‐
induce
muta5ons
that
affect
 a
phenotype
of
interest
 2)  gene5c
mapping‐
use
gene5c
crosses
to
 iden5fy
the
region
causing
the
muta5on
 3)  gene
isola5on+characteriza5on
 Gene5c
Analysis
of
evolu5on
 1)  Do
compara5ve
molecular
gene5cs
across
 different
species
 2)  transgenics
across
species
 3)  gene5c
mapping
in
between‐species
crosses
 How
do
organisms
develop?

 Results
from
Developmental
Gene5cs:
 ‘Toolkit
genes’,
transcrip5on
factors
are
 essen5al
developmental
regulators
 controlling
basic
body
plan
 Results
from
Developmental
Gene5cs:
 ‘Toolkit’
genes
are
essen5al
developmental
 regulators
controlling
basic
body
plan
 Results
from
Developmental
Gene5cs:
 ‘Toolkit’
genes
are
highly
conserved
in
 func5on!
 Results
from
Developmental
Gene5cs:
 ‘Toolkit’
genes
are
highly
conserved
in
 func5on!
 Pax6 is expressed in Drosophila and mouse eyes, functions the same way Results
from
Developmental
Gene5cs:
 ‘Toolkit’
genes
are
highly
conserved
in
 func5on!
 Implica5ons
for
morphological
 evolu5on
 •  basic
body
plan
established
early,
 developmental
regulators
remained
highly
 conserved
in
protein
sequence
and
func5on
 •  different
structures
evolved
subsequent
to
 establishment
of
basic
developmental
 regula5on
of
simpler
forms
 •  new
structures
emerged
by
‘hooking
up’
 new
structural
genes
with
exis5ng
toolkit
 genes
 •  convergent
eye
structure
evolved
from
a
 homologous
photoreceptor
organ
 •  homologous
regulatory
pathway
regulates
 very
dis5nct
structures
 Evo‐Devo:
Understanding
 Homology
 The
problem
of
evolving
novel
 forms
 •  new
genes
rarely
arise
spontaneously,
and
 most
evolu5on
involves
‘5nkering’
with
 exis5ng
genes
 •  poten5al
problems
if
genes
have
mul5ple
 func5ons‐
structural
changes
can
damage
 other
func5ons‐
pleiotropy
 How
do
novel
forms
evolve
while
 avoiding
harmful
pleiotropic
effects?
 Carroll 2005 Evolu5on
by
5nkering
with
exis5ng
 genes
 Gene
Duplica5on
and
 Divergence:
Example
of
Leaf‐ ea5ng
monkeys
 Pygathrix nemaeus Colobus guereza Study
by
Zhang
(2008):
 When
confronted
with
the
same
 adap5ve
pressures,
do
the
same
gene5c
 outcomes
occur?

 J. Zhang, EEB, University of Michigan Parallel
Adapta5on
to
leaf
diet
 •  shi[
from
fruits/insects
to
leaves
leads
to
 evolu5on
of
diges5ve
system‐
 endosymbio5c
bacteria
 •  strong
shi[
in
diges5ve
environment
 leading
to
increased
demands
for
RNAse,
 shi[
in
pH
 Parallel
Gene
Duplica5on
and
 rapid
evolu5on
of
RNAse

 Parallel
Gene
Duplica5on
and
 rapid
evolu5on
of
RNAse

 Parallel
Gene
Duplica5on
and
 rapid
evolu5on
of
RNAse

 Parallel
Gene
Duplica5on
and
rapid
 evolu5on
of
RNAse
:
 Evidence
for
pleiotropic
effects
 How
do
novel
forms
evolve
while
 avoiding
harmful
pleiotropic
effects?
 Carroll 2005 Mary Claire King Allan WIlson Morphology
Evolves
by
co‐op5ng
 exis5ng
regulatory
networks
 •  changes
in
the
5ming
(heterochrony)
or
 loca5on
(heterotropy)
of
gene
expression
 of
transcrip5on
factors
can
lead
to
changes
 in
morphology

 Morphology
Evolves
by
co‐op5ng
 exis5ng
regulatory
networks
 Carroll, S.B. 2005 •  FOXP2
expression
correlates
with
vocal
 learning
in
birds
 Carroll, S.B. 2005 ...
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