lecture_21_SW -...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: How
do
Organisms
maintain
coopera2on?

 -  rigin of cells o -  rigin of chromosomes o -  rigin of genetic code o -  rigin of sexual reproduction o -  rigin of eukaryotes o -  rigin of multicellularity o -  rigin of colonies (e.g. nonreproductive castes) o How do Genomes not ‘explode’ through transposition? 1)  Selection on rest of genome for silencing: methylation, RNAi may have evolved as host silencing mechanisms 2)  transposition-selection balance •  abundance
is
increased
by
replica2on
(i.e.
 transposi2on)
 •  abundance
is
reduced
by
natural
selec2on
 against
harmful
effects
on
the
organism
 •  final
abundance
result
of
a
balance
between
 these
two
 Transposi2on‐selec2on
balance:
 theory
 Mitochondrial
Transmission
 •  lack
of
mitosis
and
meiosis
of
organelles
sets
 up
poten2al
for
spread
of
selfish
elements
 Mitochondrial
Transmission
 •  uniparental
inheritance
strongly
reduces
 compe22on
within
individuals
 •  biology
of
uniparental
inheritance
consistent
 with
hypothesis
that
it
EVOLVED
to
maintain
 coopera2on
 How
do
Mitochondria
Stay
 Coopera2ve?
 •  maternal
inheritance
of
cytoplasmic
genes
in
 many
genomes
creates
conflict
of
interest
with
 nuclear
genome
 •  mitochondrial
muta2ons
that
enhance
 maternal
fitness
can
spread,
even
if
cost
is
 severe
to
male
fitness
 But
Uniparental
Inheritance
 Creates
NEW
conflict!
 Selfish
Cytoplasms
in
Animals
 Hurst & Warren, 2001 Coopera2on
of
Mul2cellular
organisms:
How
do
 collec2ons
of
cells
maintain
coopera2on?

 -  rigin of cells o -  rigin of chromosomes o -  rigin of genetic code o -  rigin of sexual reproduction o -  rigin of eukaryotes o -  rigin of multicellularity o -  rigin of colonies (e.g. nonreproductive castes) o •  star2ng
from
a
single
cell
reduces
compe22on
 within
individuals
 •  separa2on
of
germline
with
limited
numbers
 of
cell
divisions
inhibits
transmission
of
selfish
 cell
lineages
 •  tumor
suppressors,
other
features
inhibit
 unregulated
cell
division
 •  BUT:
soma2c
muta2on
inevitable
in
long‐lived
 mul2cellular
organisms!
 How
Do
Collec2ons
of
Cells
Stay
 Coopera2ve?
 Cancer:
Selfish
Cell
lineages
 evolving
within
an
individual
 •  spreads
commonly
in
2ssue
that
is
 rela2vely
undifferen2ated
 •  evolves
resistance
to
treatment/immune
 system
 How
Do
Individual
Genomes
Stay
so
 Coopera2ve?

 -  any features of individual organisms ensure m that the allelic competition WITHIN an individual is minimized -  nsures that many genes succeed by e enhancing the fitness of the organism (‘group’) -  UT: countless ways to evade cooperation! B -  resence of strong selection on rest of p genome seems essential to maintain higherlevel cohesion! 1)  BoWom‐up:
Starts
with
genes‐Studies
 comparing
genes
and
genomes,
molecular
 evolu2onary
and
popula2on
gene2c
 approaches
 2)  Top‐down:
Starts
with
phenotypes:
molecular
 gene2c
studies
within‐
and
between
systems
 to
understand
the
similari2es
and
differences

 Approaches
to
Studying
the
 gene2cs
of
Adapta2on
 Evo‐Devo:
 Understanding
the
Evolu2on
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
Gene2c
Analysis
 1)  mutagenesis‐
induce
muta2ons
that
affect
 a
phenotype
of
interest
 2)  gene2c
mapping‐
use
gene2c
crosses
to
 iden2fy
the
region
causing
the
muta2on
 3)  geneisola2on+characteriza2on
 Gene2c
Analysis
of
evolu2on
 1)  Do
compara2ve
molecular
gene2cs
across
 different
species
 2)  transgenics
across
species
 3)  gene2c
mapping
in
between‐species
crosses
 ...
View Full Document

This note was uploaded on 04/22/2009 for the course EEB 318 taught by Professor Cutter during the Spring '09 term at University of Toronto.

Ask a homework question - tutors are online