Transcript Mendelian Inheritance

EVOLUTION
Instructor:
Patricia Princehouse



MW 1230-1:45 pm
DeGRACE 312
Attendance Required
217 Rockefeller
440-478-5292
[email protected]
BIOL/ANTH/GEOL/HSTY/PHIL 225
Darwin
and the
Nature of
Science
Lunar Society
Lunar Society
The Mount, Shrewsbury
Maer Hall
Edinburgh
“You care for
nothing but
shooting, dogs,
and rat-catching,
and you will be a
disgrace to
yourself and all
your family”
-Robt Darwin
to 16-year-old Charles
Edinburgh
Robert Grant
Cambridge
Voyage of the Beagle
Darwin Children
Darwin Children
Darwin Children
Sir Richard Owen
Joseph
Hooker
TH Huxley
Charles Lyell
Alfred Russel Wallace
What is
Science?
The Scientific Revolution
17th Century Science

New systems: Copernican
Revolution, Galileo, Descartes,
Newton

New reliance on experiment –
formation of scientific societies
witnessing together

Separation of science from politics
(i.e. religion & government)

Renewed interest in arguments for
the existence of God, especially
the argument from design
Science since Newton:
Uses only natural explanations
(methodological materialism)
 Prefers reductionist explanations
(Ockham’s razor, parsimony)
 Addresses “How”, rather than “Why”
 Testable
 Correctible
 Extendable

The 3-fold Structure of
Science

Primary Theory (core inference)

Secondary Theories (mechanisms)

Tertiary Theories (hypotheses/scenarios)
The 3-fold Structure of Science



Core
inference
Heliocentrism
Descent with
modification






Mechanisms
Copernicus’
concentric
spheres
Kepler’s laws
Newton’s
laws
Relativity
theory
String theory






Hypotheses
/scenarios
Halley’s
comet
Eclipses
Orbit of
Mercury
Red shift
Hawking
radiation
The 3-fold Structure of Science



Core
inference
Heliocentrism
Descent with
modification






Mechanisms
Copernicus’
concentric
spheres
Kepler’s laws
Newton’s
laws
Relativity
theory
String theory






Hypotheses
/scenarios
Halley’s
comet
Eclipses
Orbit of
Mercury
Red shift
Hawking
radiation
The 3-fold Structure of Science

Core
inference




Heliocentrism





Descent

with

modification


Mechanisms
Soft Inheritance
Pangenesis
Orthogenesis
Saltationism
Natural Selection
Mutation
Genetic Drift
Gene Flow
Genomics
Allometry









Hypotheses/
scenarios
Giraffe’s neck
Mammalian ear
bones
Hardy-Weinberg
models
DDT resistance
Peppered moth
Gene families
Evo-Devo details
Lucy ancestral…
Biology
Lamarck 1744-1829
-Characteristics acquired in
response to the
environment during the
lifetime of an organism can
be passed on to its
offspring
-Separate lineages
spontaneously generate &
transmute through
progressively higher levels
of organization
“On the view that species are
Charles
Darwin
only strongly marked and
“To my varieties,
mind it accords
permanent
and that
better
withfirst
what
we know
each
species
existed
as a
of thewe
laws
impressed
onis
variety,
can
see why it
matter
byofthe
Creator, that
that
no line
demarcation
can
the production
and
be drawn
between species,
extinction
of the past
and
commonly
supposed
to have
present
inhabitants
of the
been
produced
by special
acts
world
shouldand
have
been due
of creation,
varieties
to secondary
causes.”to
which
are acknowledged
have been produced by
secondary laws.”
Charles Darwin
“Man with all his noble
qualities, with sympathy which
feels for the most debased, with
benevolence which extends not
only to other men but to the
humblest living creature, with
his god-like intellect which has
penetrated into the movements
and constitution of the solar
system –with all these exalted
powers— Man still bears in his
bodily frame the indelible
stamp of his lowly origins”
“Descended from the
apes?
My dear, we will hope
it is not true. But if it
is, let us pray that it
may not become
generally known.”
-Mrs Canon of Worchester,
1859
Poets say science takes away from the
beauty of the stars - mere globs of gas
atoms. Nothing is 'mere'. I too can see
the stars on a desert night, and feel them.
But do I see less or more? The vastness
of the heavens stretches my imagination
- stuck on this carousel my little eye can
catch one-million-year-old light. A vast
pattern - of which I am a part...
What is the pattern or the meaning or
the why? It does not do harm to the
mystery to know a little more about it.
For far more marvelous is the truth than
any artists of the past imagined it. Why
do the poets of the present not speak of
it? What men are poets who can speak of
Jupiter if he were a man, but if he is an
immense spinning sphere of methane
and ammonia must be silent?
-Richard Feynman
“There is grandeur in this
view of life, with its
several powers, having
been originally breathed
by the Creator into a few
forms or into one; and
that, whilst this planet
has gone cycling on
according to the fixed law
of gravity, from so simple
a beginning endless
forms most beautiful and
most wonderful have
been, and are being,
evolved.”
“What the
Frenchman
did for
species,
I will do for
forms.”
-Darwin, 1838 notebook
Charles Darwin
1809-1882
Heaven
Transformational
forfend me
from
Change
Lamarck
nonsense of a
vs
‘tendency to
progression’
Variational
C. Darwin
Change
Natural
Selection



Superfecundity
Small-scale, Copious,
Undirected Variation
Strong Principle of
Heredity
PROBLEM:
Nature of
Variation?
Hard
inheritance:
Soft
vs Hard
Particulate
Blending
inheritance
inheritance
Fleeming
Jenkin
Nature of Variation
Particulate inheritance
Pangenesis theory
Combined hard & soft
inheritance
Expanded by DeVries
Nature of Variation
Rediscovery of Mendel 1900
-Particulate inheritance
-Sequestration of germ plasm;
August Weismann
-Macromutation as the basis for
speciation; Hugo DeVries
-Small-scale mutation as basis
for gradual variation; TH Morgan
Nature of Variation
How Mendelism solved
Darwin’s problem:
-Distinction between
phenotype & genotype
-Discrete units of
inheritance
Genetic Theory
Mendelian Inheritance
X
F1
A sexually reproducing diploid organism
=
Mendelian Inheritance
X
F1
F1 X F1 =
F2
=
Mendelian Inheritance
X
AA
aa
=
F1
Aa
Aa
Aa
Aa
F1 X F1 = (Aa X Aa =)
F2
AA
Aa
Aa
aa
Mendelian Inheritance
X
Homozygous dominant AA
aa
=
Homozygous recessive
F1
Heterozygous
F1 X F1 =
Aa
Aa
Aa
Aa
(Aa X Aa =) heterozygote x heterozygote
F2
AA
25%
Aa
Aa
50%
aa
25%
X
Mendelian Inheritance
Punnett Square
Mother’s alleles
A
AA
aa
Father’s alleles
A
a
Aa
Aa
a
Aa
Aa
Inside the boxes are the genotypes of the offspring
X
Mendelian Inheritance
Punnett Square
Mother’s alleles
A
Aa
Aa
Father’s alleles
a
A
AA
Aa
a
aA
aa
Inside the boxes are the genotypes of the offspring
X
Mendelian Inheritance
Punnett Square
Mother’s alleles
A
Aa
aa
Father’s alleles
a
a
aA
aa
a
aA
aa
Phenotypes of the offspring:
PROBLEM:
Nature of Variation?
Hard
inheritance:
19th C: Blending
inheritance
Soft
vs Hard
inheritance
vs.
Particulate
inheritance
Fleeming
Jenkin
Mendelian Inheritance
X
-
Additive Loci
=
Mendelian Inheritance
-
Additive Loci
=
X
AA
aa
Aa
Aa
Aa
Aa
Draw a Punnett Square illustrating the genotypes of an F1 x F1 cross
Mendelian Inheritance
-
Additive Loci
=
X
Aa
AA
Aa
Aa
Aa
aa
So, what about genes in populations?
Australian Cattle Dogs
-Clinic held at the National Specialty show
-100 dogs examined by an ophthamologist
-49 are found to be affected by Progressive
Retinal Atrophy (PRA) blindness
-What is the likelihood that unaffected dogs are
carriers?
-Will the disease disappear from the population?
To deal with
genes
populations, we
Cattle
Dog in
example:
startq2with
an
oversimplified
model
= affected individuals (49/100 aa)
that preserves some important
q=?
p =?
# of non-carriers?
factors for us.
Hardy-Weinberg Theorem
p+q=1
p2 + 2pq + q2 = 1
p = frequency of dominant allele (A)
q = frequency of recessive allele (a)
Assumptions of the
Hardy-Weinberg Principle
1) Mating is random
2) Infinitely large population
3) Closed breeding colony
4) No mutation
5) Equal probability of survival & reproduction
fmi Futuyma
Significance of the
Hardy-Weinberg Principle
“Foundation on which almost all of the theory of population
genetics of sexually reproducing organisms --which is to say,
most of the genetic theory of evolution-- rests.” -Futuyma
-In the absence of perturbing factors, allele & genotype
frequencies remain constant over generations
-Not dependent on past history of the population
(first order Markov process)
-Ratios often hold in studies of natural populatons
-Deviations often demonstrate Natural Selection at work
Fisher
Haldane
Dobzhansky & Morgan
Wright
Mayr
McClintock
Natural
Selection



Superfecundity
Small-scale, Copious,
Undirected Variation
Strong Principle of
Heredity
Modern Synthesis:
4 Forces of Evolution




Natural Selection
Genetic Drift
Gene Flow
Mutation
What’s wrong
with this picture?
The Argument from Design
Natural Theology
Rev William Paley, 1802
"In crossing a heath, suppose I
pitched my foot against a stone
and were asked how the stone
came to be there, I might
possibly answer that for anything
I knew to the contrary it had lain
there forever; nor would it,
perhaps, be very easy to show
the absurdity of this answer.”
The Argument from Design
Natural Theology
Rev William Paley, 1802
"But suppose I had found a watch
upon the ground, and it should be
inquired how the watch happened
to be in that place, I should
hardly think of the answer which I
had before given, that for
anything I knew the watch might
have always been there.”
The Argument from Design
Natural Theology
Rev William Paley, 1802
"Yet why should not this answer
serve for the watch as well as for
the stone? For this reason, and
none other, viz., that when we
come to inspect the watch, we
perceive what we could not
discover in the stone, that its
several parts were put together for
a purpose."
Argument from Design
Natural Theology – Rev William Paley, 1802
Paley’s
conclusion:
“when we come
to inspect the
watch, we
perceive what
we could not
discover in the
stone, that its
several parts
were put
together for a
purpose..“
…gets extended to the stone as well…
X
Mendelian Inheritance
Punnett Square
Ee
You do it:
List genotypes of
parents & offspring in
Punnett Square form &
give the phenotypes of
each
ee
Mendelian Inheritance
Punnett Square
2 Ee pups
You do it:
What are the probable
genotypes &
phenotypes of the
parents of this litter?
3 ee pups
X
Mendelian Inheritance
Punnett Square
Mother’s alleles
A
Aa
Aa
Father’s alleles
a
A
AA
Aa
a
aA
aa
Inside the boxes are the genotypes of the offspring