Transcript PowerPoint Slides - Lyman Briggs College

The Case of
Fur Color Evolution in
Beach Mice
slide version 2.0
www.evo-ed.com
About this Case:
1.
2.
3.
4.
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6.
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Introduction
These slides are provided as a teaching resource for
the Mouse Fur Color case as described on
www.evo-ed.com. A fuller description of the case
can be found on the website.
Teaching notes can be found in the notes section
beneath each slide when viewing the slides in
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menu, choose “View” and then “Normal.”
The Natural History of
Fur Color in Beach Mice
Fact Sheet:
Peromyscus polionotus
• Common names: Beach Mouse
or Old Field Mouse.
• Location: Southeastern U.S.A.
• Habitat: Sand burrows in dunes
or old fields.
• Home-range: ~1000 m2
• Breeding: Monogamous pairbonding. Litters of 2-8 pups,
every 30 days.
• Lifespan: 9-12 months.
Fur Color:
How are populations of these sub
species distributed within the range of
the Beach Mouse?
Question: Is sub-species fur color
linked to habitat color?
1. Yes, light colored mice are found on light sand
beaches; dark colored mice are found in dark
forest/scrub habitat.
2. Yes, dark colored mice are found in light sand
beaches; light colored mice are found in dark
forest/scrub habitat.
3. No, there is no association between sub-species
fur color and habitat color.
1.5
The Spatial Distribution of Fur Color
Lighter colored sub-species live on light sand beaches;
darker colored sub-species live in darker habitat.
Question:
Assuming that ancestral populations of beach
mouse had dark brown fur, what could have
happened to explain the occurrence of lightcolored coastal sub-species?
The Ecology of
Fur Color in Beach Mice
Beach Mouse Food Facts:
Hunting Style of Predators
Predator-Prey Experiment
(The Advantage of Fur Color)
Predator-Prey Experiment
(The Advantage of Fur Color)
• Owls caught the dark
mouse first 37% of the time
• Owls caught the light mouse
first 63% of the time.
• Owls caught the dark mouse
first 64% of the time
• Owls caught the light mouse
first 36% of the time.
Predator-Prey Experiment
(Online Simulator)
• You can replicate the predator-prey
experiments yourself.
Visit: http://www.evo-ed.com/Pages/Mice/OwlandMice/OwlandMice.html
• Watch an owl catch
mice on different
soils – or play the
role of the predator
yourself and test
your hunting skills.
Regional Pattern:
Fur Color and Habitat Color
- Researchers
examined fur color in
nine beach mouse
populations.
- Fur color brightness
was significantly
correlated to soil
brightness where
each population
lived.
Predation Study – Clay Mice
(A) Two locations with different color soil where predation on clay
mice was tested. (B) Most attacks in light soil environments were on
dark mice; most attacks in dark soil environments were on light mice.
Attack on a Clay Mouse
Summary
• Evidence suggests
that fur color may
have evolved as a
result of selective
predation.
• Fur coloration matching the
habitat coloration leads to
less detection by predators
and increases the odds of
successful reproduction.
The Cell Biology of
Fur Color in Beach Mice
Anatomy of a Hair Follicle
• The hair shaft is
made of cornified
cells – that is, dead
cells filled with
keratin.
• Within the region of
matrix stem cells are
specialized pigmentproducing
melanocyte cells.
Melanocyte
cells
Image adapted from: http://www.nature.com/ng/journal/v38/n3/fig_tab/ng0306-273_F1.html
Image: http://www.dermnetnz.org/doctors/principles/images/hair-bulb.gif
Hair Color
• Two pigments.
– Eumelanin
– Pheomelanin
Pheomelanin
Eumelanin
Image: Roland Mattern
Image: Roland Mattern
Hair Color
• Dark Hair: Lots of eumelanin
• Fair Hair: More pheomelanin, less eumelanin
• Red Hair: Lots of pheomelanin
Eumelanin and Pheomelanin
Images from: www.chem.sc.edu/analytical/chem107/lab4_032205.pdf
Question:
Why do some melanocytes produce eumelanin
while others do not?
When is eumelanin produced?
• A transmembrane protein, the melanocortin1-receptor (MC1R) is stimulated by a hormone
called the alpha-melanocyte stimulating
hormone (α-msh).
• When the MC1R
protein is
stimulated by αmsh, lots of
eumelanin is
produced.
A transmembrane protein: Image 7.8 from Biology 8th Ed. (Campbell and Reece)
How is
eumelanin
produced?
• When the MC1R protein
is stimulated, it
facilitates cAMP
production (not
pictured).
• cAMP is a molecule
commonly used in the
positive regulation of
gene expression. Lots of
cAMP within a
melanocyte cell will
facilitate the expression
of at least four genes:
c(tyr), Tyrp1, Tyrp2, p
How is
eumelanin
produced?
• When cAMP is plentiful,
c(tyr), Tyrp1, Tyrp2 and
p are all expressed and
their enzymes facilitate
the biosynthetic
pathway that leads to
eumelanin production.
How is
eumelanin
produced?
• When cAMP is scarce,
c(tyr), Tyrp1, Tyrp2 and p
are not as readily
expressed.
• If only small amounts of
cAMP are present, c(tyr)
may still be expressed
and its enzyme may
facilitate the
biosynthetic pathway
leading pheomelanin
production.
How is
eumelanin
produced?
• If c(tyr) is not
adequately expressed it
is possible that neither
biosynthetic pigment
production pathway may
occur. This would result
in no pigment
production.
How is
eumelanin
produced?
(SUMMARY)
• Stimulation of MC1R
leads to lots of cAMP
production.
• cAMP leads to the
expression of at least
four genes (c(tyr),
Tyrp1, Tyrp2, p) that
are necessary in the
production of pigment.
Check Your
Knowledge:
What role does the
MC1R protein play
in facilitating the
production of
eumelanin shown in
the biosynthetic
pathway here?
Think-Pair-Share:
Knowing what you now know about
how hair pigment is made, how could
you explain the occurrence of white
hair on a cellular level?
The Genetics of
Fur Color in Beach Mice
Clicker Question:
A mutation occurs in a gene that codes for the
MC1R protein resulting in a different hair color.
What is the minimum number of nucleotides
that would need to change in order for this new
phenotype to occur?
i)
ii)
iii)
iv)
v)
0
1
2-5
6-10
Gene mutations that result in phenotype changes
only occur when larger sections of nucleotides are
inserted or deleted.
Genetics
• The section of DNA on a chromosome that
codes for a protein is called an gene.
The mc1r Gene
• The mc1r gene is located in
Chromosome #16 in
mammals.
• It codes for the MC1R
protein that is involved in
cAMP production that
stimulates the genes
involved in the synthesis of
eumelanin.
mc1r Gene Sequence
Review: DNA is made up of long strings of
nucleotides. There are four nucleotides in DNA:
Adenine (A), Thymine(T), Guanine (G) and Cytosine
(C). Amino acids are made up of a string of three
nucleotides.
The nucleotide sequence of the mc1r gene that codes
for a functional MC1R protein is shown on the next
slide.
Substitution Mutation
• A single nucleotide substitution mutation in the mc1r
gene causes a change in amino acid #67 in the MC1R
protein chain.
• When amino acid #67 is cysteine, the MC1R protein is
unable to effectively bind the α-MSH. This changes the
pigment pathway and eumelanin is not produced.
mc1r Gene Sequence
The nucleotide sequence of the mc1r gene is as follows:
5’-ATGCCCACCCAGGGGCCTCAGAAGAGGCTTCTGGGTTCTCTCAACTCCACCTCCACAGCC
ACCCCTCACCTTGGACTGGCCACAAACCAGACAGGGCCTTGGTGCCTGCAGGTGTCTGTC
CCGGATGGCCTCTTCCTCAGCCTGGGGCTGGTGAGTCTGGTGGAGAATGTGCTGGTCGTG
ATAGCCATCACCAAAAACCGCAACCTGCACTCGCCCATGTATTCCTTCATCTGCTGTCTG
GCCCTGTCTGACCTGATGGTGAGTATAAGCTTGGTGCTGGAGACGGCTATCATCCTGCTG
CTGGAGGCAGGGGCCCTGGTGACCCGGGCCGCTTTGGTGCAACAGCTGGACAATGTCATT
GACGTGCTCATCTGTGGCTCCATGGTGTCCAGTCTTTGCTTCCTTGGTGTCATTGCCATA
GACCGCTACATCTCCATCTTCTATGCATTACGTTATCACAGCATTGTGACGCTGCCCCGG
GCACGACGGGCCATCGTGGGCATCTGGGTGGCCAGCATCTTCTTCAGCACCCTCTTTATC
ACCTACTACAACCACACAGCCGTCCTAATCTGCCTTGTCACTTTCTTTCTAGCCATGCTG
GCCCTCATGGCAATTCTGTATGTCCACATGCTCACCCGAGCATACCAGCATGCTCAGGGG
ATTGCCCAGCTCCAGAAGAGGCAGGGCTCCACCCGCCAAGGCTTCTGCCTTAAGGGTGCT
GCCACCCTTACTATCATTCTGGGAATTTTCTTCCTGTGCTGGGGCCCCTTCTTCCTGCAT
CTCACACTCATCGTCCTCTGCCCTCAGCACCCCACCTGCAGCTGCATCTTTAAGAACTTC
AACCTCTACCTCGTTCTCATCATCTTCAGCTCCATCGTCGACCCCCTCATCTATGCTTTT
CGGAGCCAGG AGCTCCGCATGACACTCAGGGAGGTGCTGCTGTGCTCCTGGTGA- 3’
This genetic code results in a functional mc1r protein (resulting in dark fur).
mc1r Gene Sequence
Let’s look at what happens when ONE SPECIFIC nucleotide is changed….
5’-ATGCCCACCCAGGGGCCTCAGAAGAGGCTTCTGGGTTCTCTCAACTCCACCTCCACAGCC
ACCCCTCACCTTGGACTGGCCACAAACCAGACAGGGCCTTGGTGCCTGCAGGTGTCTGTC
CCGGATGGCCTCTTCCTCAGCCTGGGGCTGGTGAGTCTGGTGGAGAATGTGCTGGTCGTG
ATAGCCATCACCAAAAACCGCAACCTGCACTCGCCCATGTATTCCTTCATCTGCTGTCTG
GCCCTGTCTGACCTGATGGTGAGTATAAGCTTGGTGCTGGAGACGGCTATCATCCTGCTG
CTGGAGGCAGGGGCCCTGGTGACCCGGGCCGCTTTGGTGCAACAGCTGGACAATGTCATT
GACGTGCTCATCTGTGGCTCCATGGTGTCCAGTCTTTGCTTCCTTGGTGTCATTGCCATA
GACCGCTACATCTCCATCTTCTATGCATTACGTTATCACAGCATTGTGACGCTGCCCCGG
GCACGACGGGCCATCGTGGGCATCTGGGTGGCCAGCATCTTCTTCAGCACCCTCTTTATC
ACCTACTACAACCACACAGCCGTCCTAATCTGCCTTGTCACTTTCTTTCTAGCCATGCTG
GCCCTCATGGCAATTCTGTATGTCCACATGCTCACCCGAGCATACCAGCATGCTCAGGGG
ATTGCCCAGCTCCAGAAGAGGCAGGGCTCCACCCGCCAAGGCTTCTGCCTTAAGGGTGCT
GCCACCCTTACTATCATTCTGGGAATTTTCTTCCTGTGCTGGGGCCCCTTCTTCCTGCAT
CTCACACTCATCGTCCTCTGCCCTCAGCACCCCACCTGCAGCTGCATCTTTAAGAACTTC
AACCTCTACCTCGTTCTCATCATCTTCAGCTCCATCGTCGACCCCCTCATCTATGCTTTT
CGGAGCCAGG AGCTCCGCATGACACTCAGGGAGGTGCTGCTGTGCTCCTGGTGA- 3’
mc1r Gene Sequence
Let’s look at what happens when ONE SPECIFIC nucleotide is changed….
5’-ATGCCCACCCAGGGGCCTCAGAAGAGGCTTCTGGGTTCTCTCAACTCCACCTCCACAGCC
ACCCCTCACCTTGGACTGGCCACAAACCAGACAGGGCCTTGGTGCCTGCAGGTGTCTGTC
CCGGATGGCCTCTTCCTCAGCCTGGGGCTGGTGAGTCTGGTGGAGAATGTGCTGGTCGTG
ATAGCCATCACCAAAAACCGCAACCTGCACTCGCCCATGTATTCCTTCATCTGCTGTCTG
GCCCTGTCTGACCTGATGGTGAGTATAAGCTTGGTGCTGGAGACGGCTATCATCCTGCTG
CTGGAGGCAGGGGCCCTGGTGACCCGGGCCGCTTTGGTGCAACAGCTGGACAATGTCATT
GACGTGCTCATCTGTGGCTCCATGGTGTCCAGTCTTTGCTTCCTTGGTGTCATTGCCATA
GACCGCTACATCTCCATCTTCTATGCATTACGTTATCACAGCATTGTGACGCTGCCCCGG
GCACGACGGGCCATCGTGGGCATCTGGGTGGCCAGCATCTTCTTCAGCACCCTCTTTATC
ACCTACTACAACCACACAGCCGTCCTAATCTGCCTTGTCACTTTCTTTCTAGCCATGCTG
GCCCTCATGGCAATTCTGTATGTCCACATGCTCACCCGAGCATACCAGCATGCTCAGGGG
ATTGCCCAGCTCCAGAAGAGGCAGGGCTCCACCCGCCAAGGCTTCTGCCTTAAGGGTGCT
GCCACCCTTACTATCATTCTGGGAATTTTCTTCCTGTGCTGGGGCCCCTTCTTCCTGCAT
CTCACACTCATCGTCCTCTGCCCTCAGCACCCCACCTGCAGCTGCATCTTTAAGAACTTC
AACCTCTACCTCGTTCTCATCATCTTCAGCTCCATCGTCGACCCCCTCATCTATGCTTTT
CGGAGCCAGG AGCTCCGCATGACACTCAGGGAGGTGCTGCTGTGCTCCTGGTGA- 3’
mc1r Gene Sequence
Let’s look at what happens when ONE SPECIFIC nucleotide is changed….
5’-ATGCCCACCCAGGGGCCTCAGAAGAGGCTTCTGGGTTCTCTCAACTCCACCTCCACAGCC
ACCCCTCACCTTGGACTGGCCACAAACCAGACAGGGCCTTGGTGCCTGCAGGTGTCTGTC
CCGGATGGCCTCTTCCTCAGCCTGGGGCTGGTGAGTCTGGTGGAGAATGTGCTGGTCGTG
ATAGCCATCACCAAAAACTGCAACCTGCACTCGCCCATGTATTCCTTCATCTGCTGTCTG
GCCCTGTCTGACCTGATGGTGAGTATAAGCTTGGTGCTGGAGACGGCTATCATCCTGCTG
CTGGAGGCAGGGGCCCTGGTGACCCGGGCCGCTTTGGTGCAACAGCTGGACAATGTCATT
GACGTGCTCATCTGTGGCTCCATGGTGTCCAGTCTTTGCTTCCTTGGTGTCATTGCCATA
GACCGCTACATCTCCATCTTCTATGCATTACGTTATCACAGCATTGTGACGCTGCCCCGG
GCACGACGGGCCATCGTGGGCATCTGGGTGGCCAGCATCTTCTTCAGCACCCTCTTTATC
ACCTACTACAACCACACAGCCGTCCTAATCTGCCTTGTCACTTTCTTTCTAGCCATGCTG
GCCCTCATGGCAATTCTGTATGTCCACATGCTCACCCGAGCATACCAGCATGCTCAGGGG
ATTGCCCAGCTCCAGAAGAGGCAGGGCTCCACCCGCCAAGGCTTCTGCCTTAAGGGTGCT
GCCACCCTTACTATCATTCTGGGAATTTTCTTCCTGTGCTGGGGCCCCTTCTTCCTGCAT
CTCACACTCATCGTCCTCTGCCCTCAGCACCCCACCTGCAGCTGCATCTTTAAGAACTTC
AACCTCTACCTCGTTCTCATCATCTTCAGCTCCATCGTCGACCCCCTCATCTATGCTTTT
CGGAGCCAGG AGCTCCGCATGACACTCAGGGAGGTGCTGCTGTGCTCCTGGTGA- 3’
The Cytosine at position 199 has now changed to a Thymine.
Genetic Sequences at NCBI’s GenBank
• Examples of this code can be found at:
Light Fur Allele (C):
http://www.ncbi.nlm.nih.gov/nuccore/FJ389435.1
Dark Fur Allele (R):
http://www.ncbi.nlm.nih.gov/nuccore/FJ389424.1
Consequence of Mutation
A single nucleotide mutation from a Cytosine to
a Thymine changes the amino acid in position
#67 from a Arginine to a Cysteine
Amino Acid Sequence Dark Fur:
MPTQGPQKRLLGSLNSTSTATPHLGLATNQTGPWCLQVSIPDGLFLSLGLVSLVENVLVVIAITK
NRNLHSPMYSFICCLALSDLMVSISLVLETAIILLLEAGALVTRAALVQQLDNVIDVLICGSMVSSL
CFLGVIAIDRYISIFYALRYHSIVTLPRARRAIXGIWVASIFFSTLFITYYNHTAVLICLVTFFLAMLAL
MAXLYVHMLTRAYQHAQGIAQLQKRQGSTXQGFCLKGAXTLTIILGIFFLCWGPFFLHLTLIVLCP
QHPTCSCI FKNFNLYLVLIIFSSIVDPLIYAFRSQELRMTLREVLLCSW
Amino Acid Sequence Light Fur:
MPTQGPQKRLLGSLNSTSTATPHLGLATNQTGPWCLQVSVPDGLFLSLGLVSLVENVLVVIAITK
NCNLHSPMYSFICCLALSDLMVSISLVLETAIILLLEAGALVTRAALVQQLDNVIDVLICGSMVSSL
CFLGVIAIDRYISIFYALRYHSIVTLPRARRAIVGIWVASIFFSTLFITYYNHTAVLICLVTFFLAMLAL
MAILYVHMLTRAYQHAQGIAQLQKRQGSTRQGFCLKGAATLTIILGIFFLCWGPFFLHLTLIVLCP
QHPTCSCI FKNFNLYLVLIIFSSIVDPLIYAFRSQELRMTLREVLLCSW
Consequence of Mutation
The specific amino acid sequence is very important.
One mutation within the sequence can have affect
how the protein interacts with the melanocytestimulating hormone (α-MSH).
The Role of the MC1R Protein
When amino acid #67 is arginine the MC1R
protein can stimulate cAMP production
resulting in eumelanin synthesis.
The Role of the MC1R Protein
When amino acid #67 is cysteine, the MC1R protein
is unable to effectively bind the α-MSH; cAMP
production is affected. This changes the pigment
pathway and eumelanin is not produced.
Minute Paper: Protein Function
Instructions: On a piece of paper, write down an
answer to the following question. You only have
one minute to write down an answer.
Question:
How could structural differences in
proteins lead to functional differences at
the cellular level?
The Population Genetics of
Fur Color in Beach Mice
Plausible Mechanism;
Observable Pattern
• In biological research, to say that something at
the molecular or genetic level is responsible a
phenotypic trait, a plausible mechanism and
an observable relationship should be
identified.
Mechanism: Alleles of mc1r Gene
• The mc1r gene has two alleles:
Allele R
Allele C
[Arginine at pos #67]
Codes for a functional MC1R
protein.
[Cysteine at pos #67]
Codes for a non-functional
MC1R protein.
These genetic code for these two alleles differs by a
single nucleotide substitution.
Mechanism: Effect of the mc1r Gene
Review:
- When the mc1r gene
is mutated so that
position #67 is cysteine
rather than arginine,
cAMP production is low
and the intra-cellular
process that produces
eumelanin is halted.
Observable Relationship:
Genes vs. Fur Color
• There are three possible genotypes associated with
the mc1r gene:
1. RR  Arginine-Arginine: Indicates that both copies of
chromosome 16 has an arginine amino acid at position
#67 of the mc1r gene. + Eumelanin
2. CC Cysteine-Cysteine: Indicates that both copies of
chromosome 16 has a cysteine amino acid at position
#67 of the mc1r gene. - Eumelanin
3. RC  Arginine-Cysteine: Indicates that one copy of
chromosome 16 has an arginine amino acid on
position #67 of the mc1r gene; the other copy has a
cysteine in position #67 of the mc1r gene. ? Eumelanin
Observable Relationship:
Genes vs. Fur Color
• Is there a relationship between the fur color
of beach mouse individuals and the allele
combinations (genotypes) they possess?
CC homozygous = ?
RR homozygous = ?
RC heterozygous = ?
Observable Pattern:
Color Scoring
Observable Relationship:
Scoring System
Observable Pattern:
Rostrum Color
Mice with the genotype RR have the darkest
rostrum color.
Observable Pattern: All Body Parts
Hoekstra et al 2006
Question: What does the above table tell you? Does it confirm or
contradict a genetic basis for differences in fur color among
mice?
Questions:
There is a clear pattern: beach mice with the RR
genotype tend to be darker than those with the RC
or CC genotype.
1. Why is the average score for RR mice score less
than 2 for most body parts?
2. Why is the average score for CC mice greater
than 0 for most body parts?
3. RC mice are closer in fur color to RR mice than
CC mice. Does this mean that R is dominant over
C? Be prepared to explain your answer.
Question:
Differences in fur color among beach mouse
populations can be fully explained by the
relative frequency of C and R alleles present
within each population.
1.
2.
3.
4.
5.
Strongly Agree
Agree
Unsure/Confused
Disagree
Strongly Disagree
Predict Allele Frequencies
Actual Allele Frequencies
Colonize the Beach!
(Online Simulator)
• You can experiment with population phenotype
patterns with and without predation pressure.
Visit: http://www.evo-ed.com/Pages/Mice/Beach/Beach.html
• Introduce a mutation
to the population –
then introduce a
predator!
• What will happen if
you found a new
population…..
Fur color differences among beach mouse subspecies (i.e. populations) cannot be fully
explained by differences in R:C allele
frequencies. Why not?
Summary and Application Fur Color in Beach Mice
Beach Mouse Fur: Natural History
• The species Peromyscus polionotus has several
different sub-species.
• These sub-species live in different coastal and
mainland populations.
• Different populations tend
to have different fur color,
often corresponding to the
the coloration of their
habitat.
Beach Mouse Fur: Ecology
• Research suggests that beach mouse furcoloration in different habitats may have
arisen from predation pressure.
Beach Mouse Fur: Cell Biology
• Hair color is a result of eumelanin production in hair follicle
melanocytes.
• If the MC1R protein is non-functional, eumelanin is not
effectively produced.
• Eumelanin production is dependent on positive gene
regulation as facilitated by cAMP.
Beach Mouse Fur: Genetics
• The R (dark) allele becomes the C (light fur)
allele through a single nucleotide mutation in
the mc1r gene on chromosome 16.
5’-ATGCCCACCCAGGGGCCTCAGAAGAGGCTTCTGGGTTCTCTCAACTCCACCTCCACAGCC
ACCCCTCACCTTGGACTGGCCACAAACCAGACAGGGCCTTGGTGCCTGCAGGTGTCTGTC
CCGGATGGCCTCTTCCTCAGCCTGGGGCTGGTGAGTCTGGTGGAGAATGTGCTGGTCGTG
ATAGCCATCACCAAAAACTGCAACCTGCACTCGCCCATGTATTCCTTCATCTGCTGTCTG
GCCCTGTCTGACCTGATGGTGAGTATAAGCTTGGTGCTGGAGACGGCTATCATCCTGCTG
CTGGAGGCAGGGGCCCTGGTGACCCGGGCCGCTTTGGTGCAACAGCTGGACAATGTCATT
GACGTGCTCATCTGTGGCTCCATGGTGTCCAGTCTTTGCTTCCTTGGTGTCATTGCCATA
GACCGCTACATCTCCATCTTCTATGCATTACGTTATCACAGCATTGTGACGCTGCCCCGG
GCACGACGGGCCATCGTGGGCATCTGGGTGGCCAGCATCTTCTTCAGCACCCTCTTTATC
ACCTACTACAACCACACAGCCGTCCTAATCTGCCTTGTCACTTTCTTTCTAGCCATGCTG
GCCCTCATGGCAATTCTGTATGTCCACATGCTCACCCGAGCATACCAGCATGCTCAGGGG
ATTGCCCAGCTCCAGAAGAGGCAGGGCTCCACCCGCCAAGGCTTCTGCCTTAAGGGTGCT
GCCACCCTTACTATCATTCTGGGAATTTTCTTCCTGTGCTGGGGCCCCTTCTTCCTGCAT
CTCACACTCATCGTCCTCTGCCCTCAGCACCCCACCTGCAGCTGCATCTTTAAGAACTTC
AACCTCTACCTCGTTCTCATCATCTTCAGCTCCATCGTCGACCCCCTCATCTATGCTTTTCGGAGCC
AGG AGCTCCGCATGACACTCAGGGAGGTGCTGCTGTGCTCCTGGTGA-3’
Beach Mouse Fur: Population Genetics
• R:C allele frequencies explain some (but not
all) of the variation in fur color among beach
mouse sub-species.
Clicker Question:
The C  T substitution at position 199
of the mc1r gene:
A. arose by a mutation in the beach mouse populations in
response to a need for protection from predation.
B. leads to the failure of melanocytes to make an MC1R
protein.
C. arose by a mutation then increased in frequency because
it was selectively advantageous in the beach mouse
populations.
D. had no effect on the beach mouse populations.
E. produced an alternate allele that was detrimental to mice
on the white sand beaches
What was the reason for the lighter coat colors of
the mice on the white sand beaches?
A. Owls and other carnivores prey on beach mice that do
not carry the mutant allele.
B. A substitution of cysteine for arginine at position 67
of the MC1R protein.
C. A substitution of thymine for cystosine at position 199
of the mc1r gene nucleotide sequence.
D. The failure of melanocytes to lay down melanin
pigment in the cortex of hairs of the lighter colored
beach mice.
E. The poorer binding affinity for α-MSH and the lower
amount of cAMP produced by individuals with the
mutated MC1R protein.
Fact: The C (light fur) allele has not been
detected in Atlantic Coast light fur populations
of beach mouse.
Question: Were researchers wrong about the
role of the mc1r gene and the MC1R protein?
Explain your answer in
terms of:
(a) Population Genetics
(b) Molecular Genetics
(c) Cell Biology
(d) Ecology
References
•
•
The sources for the images we used in this presentation are listed below. If an image is not
listed it is believed to be Public Domain.
Did we use one of your pictures and not give you proper credit? If so, please let us know:
[email protected].
Section, Credit
Natural History:
Mouse burrow: Valerie Henry / Evo-Ed
Mice images taken from Steiner et al (2009) Molecular Biology and Evolution 26: 35-45. Range maps, Evo-Ed.
Mouse, Valerie Henry / Evo-Ed
Ecology
Title slide - Valerie Henry / Evo-Ed
Food web, Valerie Henry / Evo-Ed
Owls hunting mice in enclosures: Valerie Henry / Evo-Ed
Graph based on Belk and Smith (1996) Journal of Mammalogy 77:: 882-890.
Predation Study slide images taken from www.oeb.harvard.edu/faculty/hoekstra/PDFs/Vignieri2010Evol.pdf
Clay mouse taken from an online webinar presented by Hopi Hoekstra
Owl and Mouse, Mark Hancox;
Cell Biology
Cell mouse, Valerie Henry / Evo-Ed
Hair follicle pictures, Public Domain and Valerie Henry / Evo-Ed
Protein, Public Domain
Molecular Genetics:
Mouse and chromosomes, Evo-Ed
Chromosome pictures, Valerie Henry / Evo-Ed
Chromosomes, Evo-Ed
2D MC1R protein, Evo-Ed
Population Genetics:
Beach with mice, Valerie Henry / Evo-Ed
Mice cartoons, Evo-Ed
Graphs/Tables Summarized from Hoekstra et al. (2006) Science 313: 101-104.
Data - Hoekstra et al. (2006) Science 313: 101-104. http://www.sciencemag.org/content/313/5783/101
Summary:
Mouse, Public Domain
http://www.evo-ed.com