12/5/2012 9:01:00 PM
general pathway of eukaryotic membrane protein production.
general physiology of skin/hair pigmentation.
characterisitics of dominant alleles.
which allele in a heterozygote is dominant, given the biochemical mechanism
of action of allele products.
factors that affect how allele frequencies change over time in a population.
allele frequencies (p and q), given genotypic frequencies.
function of various MC1R alleles.
If you breed a black with a brown what would happen?
All black pigs in f1
In f2 > you get some of each but more black than browns. It stabilizes to
So the black allele is dominant of brown.
The dna with the 2 diff alleles (homologues) in the nucleus, allele transcribed
and get spliced.transcript leave the nucleus and attract the attention of
ribosomes. Ribosomes take transcripts to the ER which get translated then
packaged into vesicles that go to the golgi and then into new vesicles that
send those proteins to cell membrane. Two different receptors on the cell
because there is two different allele in the cell
Pigment production results from the production of melanin,
2 kinds: black melanin and red/yellow melanin (no brown)
melanin is produced by melanocytes and packed into sub cellular organelles
called melanosomes, which get exported
melanocytes pack melanosome with melanin then export it to skin cells and
hait follicle cells > they will get pigmented.
Brown is the mixture of red and black
The protein MC1R (membrane receptor) sits in the membrane and makes
black melanin if cyclec AMP levels are high. High cyclic amp makes black
In response to hormone, cyclic amp levels fall and red melanin is produced
So cells can make either one if just depends on cyclic amp levels
So brown allele can switch on and off Cyclic amp levels are high all the time with B (black) allele. It is insensitive
to hormones in the environment.
In a hetrozygote, there is brown allele and black allele in the same cell. The
receptors on the cells are two different types because there are two different
Cyclic amp levels are always high because of the black allele > that is
dominance because interaction with gene products
Dominance occurs at the level of bio chemistry
The active allele (black ) never inhibits the recessive one
In heterozygotes, the allele that is on all the time, that is the one that
determines the phenotype of the offspring therefore that is the dominant
In homozygotes, the red allele is off all the time (cyclic amp levels are
The idea that there is an allele that is always dominant is not necessary
Dominance and recessiveness happens between any two particular allele at
a particular time
Any allele isn‟t necessarily only dominant all the time. It depends on what
the other allele its with in a hetrozygote
In a population if a dominant allele is common and recessive allele is rare,
the allele frequency doesn‟t change.
If recessive allele is common and the dominant allele is rare, the allele
frequency also doesn‟t change very much. The dominant frequency increases
In a large population, in the absence of selection, the starting allele
frequency influences future allele frequencies.
There is nothing inherent about dominance that causes it to increase in
frequency in a population. The dominant allele is not necessarily the most
fit allele in a population (not always increase in frequency)
A recessive allele doesn‟t doom it to a noticeable decrease
These are not in themselves sufficient enough to drive allele frequency.
We use the punnet square in a large scale to make predictions of allele
frequency and use the product rule to predict offspring genotype. 12/5/2012 9:01:00 PM
conditions necessary for Hardy-Weinberg equilibrium
whether a population is in HWE, given observed genotype or phenotype
effect of selection on changes in allele frequency
relative vs absolute fitness
how to calculate relative fitness
how to quantify strength of selection
relationship between dominance/recessiveness of alleles and response to
effect of heterozygote advantage on genetic variation
why the amount of genetic variation in a population is important
different types of selection (stabilizing, directional) and their effect on
allele is recessive to another allele doesn‟t necessarily mean it will decrease
in frequency. Evolution a change in allele frequency from one generation to
Mc1R- lots of different allele.
To recognize whether a population is evolving (eg due to natural selection)
we need something to compare it too > the conditions of HWE
Population that very large, where mating is random, mutations are rare, no
gene flow, and no selection on the population (all have equal fitness) then
we can use the allele frequency of a population to calculate the expected
genotype frequencies. > we get the HW proportions.
Genotype frequencies are predictable through allele frequencies
Classic HWE in a population for 2 alleles at a locus = 25% GG, 50% Gg, 25
Not all populations are in HWE.this tells you one or more of the conditions is
not being met (it may be evolving)
Even if two allele frequencies are equal, that doesn‟t determine that the
population is in HWE
Population is in HWE (no evolutionary forces are operating on the
population) > allele frequency is not changing population from one
generation to the next If expected allele frequency is different from observed allele frequency then
the population is not in HW. > this means that one or more of the conditions
in not being met. The population could be evolving.
Dominance does interact with selection pressure
When selection occurs on a dominant allele, it can wipe out that allele pretty
fast. But selection against a recessive allele, there always gna be a copy of
that recessive allele in a heterozygous individual. Heterozygotes have
normal personal fitness because deleterious allele is recessive
Dominant allele will reach a high final frequency (even heterozygotes have
high fitness) but will never reach a frequency of 1. Deleterious rec allele will
still exsist in a population because it is “sheltered” in heterozygotes
Conversely, if there is a beneficial recessive allele that arise (a mutation) will
eventually completely outcompete the unfavourable dominant allele and
reach a frequency of 1. Dominance status allele does interact with natural
selection and affect the ultimate outcome of selection. This explains why the
vast majority of genetic disorders are associated with recessive allele.
Theres hardly any genetic disorders associated with dominant allele. This is
because if there were, natural selection would take them out of the
Selection > most important evolutionary force in biology
Different types of selection would have diff effects on the amount of genetic
variation in a population .
Genetic variations meant by how many diff alleles are there in a population.
Another measure is hetrozygoucity. What proportion of indivisuals in the
population are heterozygotes at a given locus
Why do we care about genetic variation (long term and short term) > if a
population lack genetic variation it can not adapt to a changing environment.
Its also important at an individual level.
Inbreeding depression > offspring of close relatives have low fitness because
Deleterious recessive allele.
If selection favoured heterozygotes. Both alleles will be maintained in the
population in equal frequency. Selection without evolution >> hetrozygote
advantage.(because allele frequency is not changing)
The vat majority of traits is not governed ( that affect fitness) by a single
locus rather quanitative traits distribution. Selection have affect on genetic variation as well as population mean value
for the trait under selection
Most traits that are under stabilizing selection the most common form of
selection. Eg. Baby birth weights..The individuals with extreme phenotypes
(smaller or lager than average) have low survivorship than those that had
the average value.
Directional selection > the indivisuals at one extreme are favoured. This
causes a shift in the population mean value, unlike the stabilizing selection
where mean value stays the same and the variation (scatter) around that in
terms of the phenotypes shrinks
Directional> favours indivisuals with an extreme (eg. Tail length)
Directional selection eventually become stabilizing selection? Yes. 12/5/2012 9:01:00 PM
effect of various types of selection on amount of variation in a population.
examples of stabilizing, directional, disruptive.
reasons why directional selection does not remove all genetic variation from
characteristics, and examples, of frequency dependent selection.
reasons why all living things are not perfectly adapted to their environment.
effect of genetic drift on allele frequencies within a population, particularly in
the case of bottlenecks etc.
effect of genetic drift on variations between populations.
mechanism that explain why mutation is NOT directed toward the needs of
general fitness effects of mutations.
why most mutations that affect fitness are harmful.
effect of gene flow on allele frequencies.
characteristics of adaptive vs. non-adaptive mechanisms affecting allele
how various evolutionary forces reinforce or oppose one another.
Why do population evolve? > natural selection but its not the only thing that
cause population to evolve
*how is this force likely to affect allele freq in a population
*how is this force likely to affect the total amount of genetic variation in a
population. (the total standing of genetic variation in a population)
3 modes of selection on the quantitative traits: 1.stabilizing the most wide
spread of selection. 2. Directional selection (one extreme is favored over
everyone else) (eg. Fast runner cheetah over slow runner)
why is there still genetic variation then when it comes to directional
variation? Because the environment changes. Selection presuure are not
always uniform, it can vary over time. So both alleles are maintained
because selection pressure varies temporarily.
Selection pressure also vary in a special manner. Environments are not
uniform. One range changes from the other range.
Selection is the only force that results in adaptations. Adaptation is any trait
that increases the fitness of the individual relative to the other individual in
the population. So adaptations are relative (involve differences in relative
fitness) and environment specific. Adaptations are specific to a particular environment
The final type of selection is disruptive. This is the opposite of stabilizing
selection. (the individual with intermediate phenotypes/ average having the
highest fitness) In disruptive selection, the indivisuals in either extreme are
favoured. There isn‟t a shift in population mean value, but there is
discontuity arising. Selection pushes the population towards two separate
peaks in population.
In frequency dependent selection, the fitness of a particular phenotype or a
genotypes is gna depend on relative frequency of the population.
-ve frequency selection > advantage of being rare (eg. Predators/ prey)
over a long period of times > -ve frequency selection will result in both
alleles in a population to be maintained. (balanced) the selective advantage
will make them more common in a population and it will no longer have the
“rare” advantage (eg. rare male mating advantage)
the opposite ( not as wide spread) is +ve frequency dependence selection.
Selective adv to the most common phenotype in the population. ( usually
due predator‟s prior experience)
the adv to the common form will cause the more common allele to replace
the other allele in the population
Selection results in adaptation in populations but it never results in
perfection in the environment:
trade off> trait may be beneficial in one context but harmful in another
context. There will always be compromising between competing demands.
Its constraited by the available genetic variation.
Selection constrainted by the doiminance relationship of alleles
Environment is always changing
Selection is the only ADAPTIVE evolutionary force that drives allele
Other conditions of HWE: (unadaptive evolutionary force)
Population size has to be really big for a population to be in HWE. The
smaller the population is the more heavily it will be influenced by genetic
Genetic drift > random unpredictable changes in allele frequency due to
sampling error (unlike selection in the term of unpredictable and random)
Reduction in population size > bottleneck Genetic drift causes one allele goes to fixation (1) and all the other alleles
are lost from the population, low genetic diversity
Genetic drift opposes the affect of selection. Depends how strong selection is
towards a particular allele and the population size. Small population size drift
outways the effect of selection. Vise vera
Genetic drift decreases variation within a population.
Genetic drift increases variation among populations.
Mutation is important primarily because it is the new source of genetic
variation. It creates new alleles.
Mutation is not random (predictable thru biochemical laws etc. ) but it is not
directed towards the needs of the organism in the environment
Most mutations have neutral effects on fitness. The ones that do are harmful
Mutation works in opposition to selection. But it provides raw material for
Gene flow (migration) movement of alleles between populations. It can
introduce alleles that are new to a population. (mutation is ultimately the
original source of genetic variation but gene flow can move existing alleles
from on population to another)
Gene flow can oppose local selective forces
Selection-migration balance, preventing population from adapting to their
*which have similar effects on genetic variation within a population?
* on differences between population?
2 types of mating that is not “random:
- inbreeding or inbreeding avoidance
- assortative or dissassortative mating why evolution is true
types of non-random mating
effect of non-random mating on HWE and on evolution
characteristics of a scientific theory
components of the theory of evolution
evidence for "descent with modification"
examples of homology and why they support the idea of evolution
examples of vestigial traits and why they support the idea of evolution
role of fossil record as evidence for evolution
one of the conditions for a population in HWE is random mating. But this
hardly true. 2 types of mating. Assortative mating (more common) or
if heterozygotes only mate with hetro, half will be hetro but quarter will be
homo and the other quarter will be homo
what happens when a population mates non randomly? > taks the
population out of HWE but it doesn‟t cause a change allele frequency so it
doesn‟t result in evolution.
What do scientists mean by theory? A coherent set of testable hypotheses
that attempt to explain facts about the natural world. Darwins theory of
evolution is a theory. Makes predictions of the natural world.
What is meant by true in science? If there is so much evidence that it would
be perverse to deny it
Difference between theory and a fact. Theory is alleviated to be considered a
fact only after they‟ve been tested in many diff ways and non of those test
resulted in the theory to be falsified. A statement that cannot possibly
falsified is not a scientific theory.