!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
Educator Materials!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*1*of*8
!
INTRODUCT IO N !T O!THE!MOLECULAR!GENETICS!OF!THE!!
COLOR!MUTATIONS!IN!ROCK!POCKET!MICE!
!
OVERVIEW!!!
These%lessons%serve%as!an%extension%to%the%Howard%Hughes%Medical%Institute%short%film%The!Making!of!the!Fittest:!
Natural!Selection!and!Adaptation.!Students%w ill%transcribe %and %tran slate%p ortion s%of%th e%w ild-ty pe %and %m uta nt%ro ck%
pocket%mouse%Mc1r!gene.%By%comparing%DNA%sequences,%students%identify%the%locations%and%types%of%mutations %
responsible%fo r%the%co at-color%change%described%in%the%film.%Students%will%answer%a%series%of%questions%to%explain%
how%a%change%in%amino%acid%sequence%affects%the%functionality%of%the%MC1R%protein,%and%how%that%change%might%
directly%affect%the%coat%color%of%the%rock%pocket%mouse%populations%and%the%survival%of%that%population.%
!
KEY!CONCEPTS!AND!LEARNING!OBJECTIVES!!
• A%mutation%is%a%random%change%to%an%organism’s%DNA%sequence.%
• Most%mutations%have%no%effect%on%traits,%but%some%mutations%affect%the%expression%of%a%gene%and/or%the%
gene%product.%
• The%environment%contributes%to%determining%whether%a%mutation%is%advantageous,%deleterious,%or%neutral.%
• Natural%selection%preserves%favorable%traits.%
• Variation,%selection,%and%time%fuel%the%process%of%evolution.%
• Both%the%type%of%the%mutation%and%its%location%determine%whether%or%not%it%will%have%an%effect%on%
phenotype%(advanced%version%only).%
Studen ts %will%be%able%to:%
• transcribe%and %transla te%a%D NA %seq ue nce.%
• connect%DNA%changes%to%phenotype.%
• analyze%and%organize%data.%%
%
CURRICULUM!CONNECTIONS!
%
Curriculum!
Standards!
NGSS%(April%2013)%
HS-LS1-1,%HS-LS3-1,%HS-LS3-2,%HS-LS4-2,%HS-LS4-4,%HS-LS4-5%
HS.LS1.A,%HS.LS4.B,%HS.LS4.C%
Common%Core%(2010)%
CCSS.ELA-Literacy.RST.9-10.3,%CCSS.ELA-Literacy.RST.9-10.4,%
CCSS.ELA-Literacy.RST.9-10.7%
AP%Biology%(2012–13)%
1.A.1,%1.A.2,%3.A.1,%3.C.1,%4.B.1%
IB%Biolog y %(2 0 09 )%
3.5,%4.1,%4.3,%5.4,%7.3,%7.4,%D.2,%G.1%
%
KEY!TERMS!!
evolution,%natural%selection,%variation,%trait,%mutation,%adaptation%
!
TIME!REQUIREMENT!!
These%activities%are%designed%for%one%50-minute%class%period%including%showing%the%film.%Additional%time%for%the%
analysis%questions%might%be%required%for%homework%depending%on%students’%pace.%Both%activities%cover%the%same%
material,%but%activity%2%has%additional%material%covering%intracellular,%transmembra ne ,%and %extrac ellular%d om a ins.%
%
%
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*2*of*8
!
SUGGESTED!AUDIENCE!
Activity%1:%The%activity%is%designed%for%high%school%biology%(primarily%first-year%biology,%both%regular%and%honors).%
Activity%2:%The%activity%is%designed%for%AP%and%IB%high%school%biology%and%introductory%college%biology.%
!
PRIOR!KNOWLEDGE!!
Students%should%be%familiar%with%the%definitions%of%“gene”%and%“protein.”%They%should%also%be%comfortable%with%
basic%molecular%genetics,%including%a%familiarity%with%the%processes%of%transcription%and%translation.%Finally,%
students%should%understan d%that%a%protein’s%amino%acid%sequence%determines%its%structure,%which%determines%its%
function.%
!
MATERIALS!!
Students%will%need:%
genetic%code%chart%(provided%in%student%m ateria ls)%
blue,%red,%and%green%colored%pencils!
!
TEACHING!TIPS!
• If%you%do %n ot%have%acce s s%to %a %c o lo r%p r in te r%t o %p rin t%t h e %ch a rt %o n %page%2%of%this%document,%you%should%
compare%students’%work%to%how%the%charts%below%appear%on%your%computer%screen.%
• You%could%assign%analysis%questions%as%homework%to%reduce%the %am o un t%of%class%tim e%req u ired%fo r%this%
lesson.%
!
ANSWER!KEY!ACTIVITY!1!
GENE!TABLE!1:!WILD-TYPE!MC1R!GENE!(LIGHT!COAT-COLOR!PHENOTYPE)!
%
015'
%
%
%
%
%
%
022'
DNA%
TTG%
AGG%
TGG%
GCG%
TGT%
CCG%
CAA%
GGA%
mRNA%
AAC!
UCC!
ACC!
CGC!
ACA!
GGC!
GUU!
CCU!
Amino%
Acid%
Asn!
Ser!
Thr!
Arg!
Thr!
Gly!
Val!
Pro!
%
%
105'
'
'
'
'
'
'
112'
DNA%
CGG%
GAC%
CGG%
TGG%
GCC%
CAC%
TGA%
CAC%
mRNA%
GCC!
CUG!
GCC!
ACC!
CGG!
GUG!
ACU!
GUG!
Amino%
Acid%
Ala!
Leu!
Ala!
Thr!
Arg!
Val!
Thr!
Val!
%
%
154'
'
'
'
'
'
'
161'
DNA%
TCA%
TAA%
CAC%
TGT%
GAC%
GGG%
GCC%
CGA%
mRNA%
AGU!
AUU!
GUG!
ACA!
CUG!
CCC!
CGG!
GCU!
Amino%
Acid%
Ser!
Ile!
Val!
Thr!
Leu!
Pro!
Arg!
Ala!
%
'
209'
'
'
212'
DNA%
GTG%
TAC%
GAA%
CGT%
mRNA%
CAC!
AUG!
CUU!
GCA!
Amino%
Acid%
His!
Met!
Leu!
Ala!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*3*of*8
!
%
'
230'
'
'
'
'
'
'
237'
DNA%
GAA%
CAG%
GTG%
GTT%
CCA%
AAG%
GCT%
GAG%
mRNA%
CUU!
GUC!
CAC!
CAA!
GGU!
UUC!
CGA!
CUC!
Amino%
Acid%
Leu!
Val!
His!
Gln!
Gly!
Phe!
Arg!
Leu!
!
GENE!TABLE!2:!MUTANT!MC1R!GENE!(DARK!COAT-COLOR!PHENOTYPE)!
%
015'
%
%
%
%
%
%
022'
DNA%
TTG%
AGG%
TGG%
ACG%
TGT%
CCG%
CAA%
GGA%
mRNA%
AAC!
UCC!
ACC!
UGC!
ACA!
GGC!
GUU!
CCU!
Amino%
Acid%
Asn!
Ser!
Thr!
Cys!
Thr!
Gly!
Val!
Pro!
%
% '
105'
'
'
'
'
'
'
112'
DNA%
CGG%
GAC%
CGG%
TGG%
ACC%
CAC%
TGA%
CAC%
mRNA%
GCC!
CUG!
GCC!
ACC!
UGG!
GUG!
ACU!
GUG!
Amino%
Acid%
Ala!
Leu!
Ala!
Thr!
Trp!
Val!
Thr!
Val!
%
'
154'
'
'
'
'
'
'
161'
DNA%
TCA%
TAA%
CAC%
TGT%
GAC%
GGG%
ACC%
CGA%
mRNA%
AGU!
AUU!
GUG!
ACA!
CUG!
CCC!
UGG!
GCU!
Amino%
Acid%
Ser!
Ile!
Val!
Thr!
Leu!
Pro!
Trp!
Ala!
%
%
209'
'
'
212'
DNA%
GTG%
TAC%
GAG%
CGT%
mRNA%
CAC!
AUG!
CUC!
GCA!
Amino%
Acid%
His!
Met!
Leu!
Ala!
%
'
'
'
230'
'
'
'
'
'
'
'
237'
DNA%
GAA%
CAG%
GTG%
GTG%
CCA%
AAG%
GCT%
GAG%
mRNA%
CUU!
GUC!
CAC!
CAC!
GGU!
UUC!
CGA!
CUC!
Amino%
Acid%
Leu!
Val!
His!
His!
Gly!
Phe!
Arg!
Leu!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*4*of*8
!
QUESTIONS!ANSWER!KEY!
1.!In!gene!e x p re ss io n ,!which!enzyme!is!responsible!for!transcribing!the!DNA!sequence!into!mRNA!by!adding!
complementary!RNA !nucleotides?!RNA!polymerase!
2.!In!a!euka r yo t ic!c ell,!where!does !tr a n sc rip tio n !o cc u r? !In!th e !n u c le u s!
3.!Describe!the!process!of!translation.!!
Translation!is!the!process!of!turning!instructions!from!mRNA!into!chains!of!amino!acids.!It!occurs!in!the!
cytoplasm!with!the!help!of!ribosomes!and!tRNA.%
4.!In!a!euka r yo t ic!c ell,!what!main !o rg a n e lle!is !in v olv e d !in !tra n s la tio n ?!Ribosome!
5.'Explain!the!relationship!between!DNA!sequence,!amino!acid!sequence,!and!protein!structure!and!function.'
Students!may!simply!relate!DNA!sequence!to!amino!acid!sequence,!and!amino!acid!sequence!to!the!three-
dimensional!shape!of!the!protein.!An!example!of!a!student!response!may!be:!“DNA!sequence!provides!the!code!
for!the!amino!ac id!seq uen ce.!Th e!amino!acid!sequence!d eter m ines!th e!struc ture !of!the!pr otein,!which!affects!
the!function!o f!the!p rote in.”!
6.!The!Mc1r!gene!codes!for!the!melanocortin!1!receptor!(MC1R)'protein.!
7.!If!the!MC1R!protein !is !31 7 !a mino!acids!long,!why!are!there!954!base!pairs!in!the!coding!region!of!the!gene?!
Each%of%the%amino%acids%has%a%corresponding%mRNA%codon%and%DNA%triplet%consisting%of%a%three-base%sequence.%A%
protein%that%has%317%amino%acids%therefore%has%a%DNA%base%sequence%consisting%of%951%base%pairs%(317 %×%3%=%951%
base%pairs).%The%three%additional%base%pairs%correspond%to%a%stop%codon%for%which%there%is%no%complementary%
amino%acid.%The%stop%codon%signals%the%termination%of%translation.%
8.!Of!the!five!mutations!you!identified!in!the!Mc1r!gene,!how!many!are:!
% 5%substitutions;%0%insertions;%0%deletions%
9.'Of!the!five!mutations!you!identified!in!the!Mc1r!gene,!how!many!are:!
% 1%silent;%4%missense;%0%nonsense%
10.'Mice!with!the!wild-type!(nonmutant)!Mc1r!gene!have!light-colored!fur.!Which!pigment!is!responsible!for!this!
coloration?!Pheomelanin!
11.'Using!the!information!in!the!in tro d u ct io n!on!mutations!and!your!knowledge!of!proteins,!develop!a!hypothesis!
to!explain!how!the !chan ge s!in!the!M C 1R !protein ’s!am ino!a cid!seq uen ce!m igh t!affect!its!fun ction.!
Sample!answer:!The!four!missense!mutations!in!the!Mc1r!gene!change!the!amino!acid!sequence!of!the!MC1R!
protein,!which!changes!the!structure!of!the!protein.!The!change!in!protein!structure!will!affect!the!protein!
function.!
12.!Explain!how!silent!mutations!affect!the!structure!and!function!of!the!protein.!
Silent!mutations!do!not!change!the!amino!acid,!and!the refo re !w ill!not!cha ng e!the !structure!of!the!protein.!
Because!a!protein’s!structure!is!relate d !to!its!fun ction ,!silent!mutations!do!not!affect!the!function!of!the!
protein.!
13.!Using!the!information!provided!in!the!introductio n!u n d e r!“MC1R!Gen e , ”!explain!how!the!mutant!MC1R!protein!
directly!affects!a!rock!pocket!mouse’s!coat!color.!!
The!amino!acid!changes!in!the!MC1R!protein!may!change!the!structure!and!function!of!the!protein.!This!leads!
to!increa se d !p r o d u ct io n !o f!e u melanin,!w h ic h !re s u lts !in !th e !d a rk !c o lo r . !
14.!Mutations!are!a!source!of!genetic!variation.!In!the!film,!Dr.!Carroll!says!that!mutations!occur!randomly.!What!
does!that!mean?!
Sample!answer:!It!means!that!mutations!do!not!occur!for!a!purpose!or!for!any!predetermined!result.!
15.!It!is!a!co mmon!m isc o n ce p tio n !th a t !“a ll!mutations!a r e!b a d .” !U s e!t h e!e x a m p le !o f!r oc k!p o c ke t!mice!to!exp lain !
why!this!is!not!true.!In!your!answer,!explain!how!the!dark!coat!color!mutation!can!be!an!advantage!to!some!mice!
and!a!disadvantage!to!others.!!
Sample!answer:!Mutations!can!result!in!new!traits.!The!selective!advantage!provided!by!a!trait!depends!on!the!
environment.!For!example,!on!a!light!substrate,!individuals!with!dark-colored!coats!would!be!at!a!disadvantage!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*5*of*8
!
because!they!would!stand!out!more!than!individuals!with!light-colored!coats,!making!them!easier!for!predators!
to!spot.!How ev er,!in!the !da rk!lav a!flow !ha bita t,!those !sam e !da rk-colored!individuals!would!have!a!selective!
advantage!because!they!would!be!better!camouflaged!than!light-colored!individuals.!So,!the!statement!that!“all!
mutations!are!bad”!is!incorrect,!because!there!are!different!selective!pressures!on!the!traits!produced!by!
mutations!depending!on!the!habitat.!There!are!also!silent!mutations!that!do!not!change!the!resulting!protein;!
these!are!ne utra l,!neithe r!go od !no r!ba d.!
16.!Use!your!understanding!of!evolution!and!the!information!in!the!film!to!explain!how!the!dark-colored!mutation!
came!to!be!so!common!in!some!po pulations!of!rock!pocket!mice.!Be!specific.!!
Sample!answer:!The!dark-colored!mouse!has!a!selective!advantage!in!a!hab it a t!s u ch !a s !th e !P in a c a te !la v a !f lo w,!
which!has!a!dark-colored!substrate.!Since!rock!pocket!mice!reproduce!quickly!and!often,!the!frequency!of!this!
favored!trait!wo uld!sp rea d!rap idly!throu gh !the!po pu lation.!A ny!light-colored!mice!in!the!dark-colored!habitat!
would!be!at!a!selective!disadvantage,!thus!decreasing!their!gene!frequency!in!future!generations.!In!this!way,!
favorable!traits!accum ulate!and!increase!in!frequency—just!as!Dar w in !ex p lain e d .!
!
ANSWER!KEY!ACTIVITY!2!
GENE!TABLES!
WILD-TYPE!MC1R!GENE!(LIGHT-COLORED!COAT!PHENOTYPE)!!!!!!! ! ! ! ! ! ! !!!!!!
!
%
%
015%
%
%
%
%
%
%
%
%
024%
%
DNA%
TTG%
AGG%
TGG%
GCG%
TGT%
CCG%
CAA%
GGA%
GTG%
GAG%
EXTRACELLULAR!DOMAIN!I!
!
mRNA%
AAC!
UCC!
ACC!
CGC!
ACA!
GGC!
GUU!
CCU!
CAC!
CUC!
Amino%
Acid%
Asn!
Ser!
Thr!
Arg!
Thr!
Gly!
Val!
Pro!
His!
Leu!
MUTANT!MC1R!GENE!(DARK-COLORED!COAT!PHENOTYPE)!
%
%
015%
%
%
%
%
%
%
%
%
024%
DNA%
TTG%
AGG%
TGG%
ACG%
TGT%
CCG%
CAA%
GGA%
GTG%
GAG%
mRNA%
AAC!
UCC!
ACC!
UGC!
ACA!
GGC!
GUU!
CCU!
CAC!
CUC!
Amino%
Acid%
Asn!
Ser!
Thr!
Cys!
Thr!
Gly!
Val!
Pro!
His!
Leu!
%
%
WILD-TYPE!MC1R!GENE!(LIGHT-COLORED!COAT!PHENOTYPE)!!!!!!! ! ! ! ! ! ! !!!!!!
!
%
%
105%
%
%
%
%
%
%
%
%
114%
%
DNA%
CGG%
GAC%
CGG%
TGG%
GCC%
CAC%
TGA%
CAC%
CAT%
GTC%
EXTRACELLULAR!DOMAIN!III!
!
mRNA%
GCC!
CUG!
GCC!
ACC!
CGG!
GUG!
ACU!
GUG!
GUA!
CAG!
Amino%
Acid%
Ala!
Leu!
Ala!
Thr!
Arg!
Val!
Thr!
Val!
Val!
Gln!
MUTANT!MC1R!GENE!(DARK-COLORED!COAT!PHENOTYPE)!
%
%
105%
%
%
%
%
%
%
%
%
114%
DNA%
CGG%
GAC%
CGG%
TGG%
ACC%
CAC%
TGA%
CAC%
CAT%
GTC%
mRNA%
GCC!
CUG!
GCC!
ACC!
UGG!
GUG!
ACU!
GUG!
GUA!
CAG!
Amino%
Acid%
Ala!
Leu!
Ala!
Thr!
Trp!
Val!
Thr!
Val!
Val!
Gln!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*6*of*8
!
%
WILD-TYPE!MC1R!GENE!(LIGHT-COLORED!COAT!PHENOTYPE)!!!!!!! ! ! ! ! ! ! !!!!!!
!
%
%
154%
%
%
%
%
%
%
%
%
163%
%
DNA%
TCA%
TAA%
CAC%
TGT%
GAC%
GGG%
GCC%
CGA%
GCC%
ACC%
INTRA C E LL U L A R !D OMAIN!I!
!
mRNA%
AGU!
AUU!
GUG!
ACA!
CUG!
CCC!
CGG!
GCU!
CGG!
UGG!
Amino%
Acid%
Ser!
Ile!
Val!
Thr!
Leu!
Pro!
Arg!
Ala!
Arg!
Trp!
MUTANT!MC1R!GENE!(DARK-COLORED!COAT!PHENOTYPE)!
%
%
154%
%
%
%
%
%
%
%
%
163%
DNA%
TCA%
TAA%
CAC%
TGT%
GAC%
GGG%
ACC%
CGA%
GCC%
ACC%
mRNA%
AGU!
AUU!
GUG!
ACA!
CUG!
CCC!
UGG!
GCU!
CGG!
UGG!
Amino%
Acid%
Ser!
Ile!
Val!
Thr!
Leu!
Pro!
Trp!
Ala!
Arg!
Trp!
%
WILD-TYPE!MC1R!GENE!(LIGHT-COLORED!COAT!PHENOTYPE)!!!!!!! ! ! ! ! ! ! !!!!!!
!
%
%
208%
%
%
%
212%
%
%
%
%
%
DNA%
CAC%
GTG%
TAC%
GAA%
CGT%
TRANSMEMBRAN E!V!
mRNA%
GUG!
CAC!
AUG!
CUU!
GCA!
Amino%
Acid%
Val!
His!
Met!
Leu!
Ala!
MUTANT!MC1R!GENE!(DARK-COLORED!COAT!
PHENOTYPE)!
%
%
208%
%
%
%
212%
DNA%
CAC%
GTG%
TAC%
GAG%
CGT%
mRNA%
GUG!
CAC!
AUG!
CUC!
GCA!
Amino%
Acid%
Val!
His!
Met!
Leu!
Ala!
%
WILD-TYPE!MC1R!GENE!(LIGHT-COLORED!COAT!PHENOTYPE)!!!!!!! ! ! ! ! ! ! !!!!!!
!
%
%
230%
%
%
%
%
%
%
%
%
239%
%
DNA%
GAA%
CAG%
GTG%
GTT%
CCA%
AAG%
GCT%
GAG%
TTT%
CCG%
INTRA C E LL U L A R !D OMAIN!III!
!
mRNA%
CUU!
GUC!
CAC!
CAA!
GGU!
UUC!
CGA!
CUC!
AAA!
GGC!
Amino%
Acid%
Leu!
Val!
His!
Gln!
Gly!
Phe!
Arg!
Leu!
Lys!
Gly!
MUTANT!MC1R!GENE!(DARK-COLORED!COAT!PHENOTYPE)!
%
%
230%
%
%
%
%
%
%
%
%
239%
DNA%
GAA%
CAG%
GTG%
GTG%
CCA%
AAG%
GCT%
GAG%
TTT%
CCG%
mRNA%
CUU!
GUC!
CAC!
CAC!
GGU!
UUC!
CGA!
CUC!
AAA!
GGC!
Amino%
Acid%
Leu!
Val!
His!
His!
Gly!
Phe!
Arg!
Leu!
Lys!
Gly!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*7*of*8
!
QUESTIONS!ANSWER!KEY!
1.!Using!the!amino!acid!location!numbers!provided!above!the!first!and!last!column!of!each!table,!list!the!locations!
of!the!five!amino!acids!that!contain!a!mutation.!!
The!amino!acid!locations!are!018,!109,!160,!211,!and!233.!!
2.!Of!the!five!mutations!you!identified!in!the!Mc1r!gene,!how!many!are!the!following:!
! 5!substitutions,%0%insertio n s ,%0!deletions%
3.!Of!the!five!mutations!you!identified!in!the!Mc1r!gene,!how!many!are!the!following:!
! 1!silent,%4%missense,%0%nonsense%%
4.'' '
' a.!Which!four!amino!acid!locations!(see!Question!1!above)!contain!the!missense!mutations?!
The!amino!acids!are!018,!109,!160,!and!233.!
b.'Explain!the!link!between!DNA!sequence!and!protein!structure!and!function .!
Students!may!simply!relate!DNA!sequence!to!amino!acid!sequence,!and!amino!acid!sequence!to!the!three-
dimensional!shape!of!the!protein.!More-advanced!students!should!be!able!to!link!the!mutation!to!a!change!in!
the!protein’s!prim a ry!structure,!which!affects!other!levels!of!structure!(secondary!and!tertiary).!All!student!
responses!should!de m onstrate !an!und erstan ding!of!the!link!betw ee n!DN A!an d!the!seq uen ce!of!am ino!acids!
that!determ ine s!the !struc ture ,!and !the re fore !fun ction ,!of!a!pro tein .!
5.!Using!the!information!on!mutations!in!the!introduction!and!your!knowledge!of!proteins,!develop!a!hypothesis!to!
explain!how!the!changes!in!the!MC1R!protein’s!amino!acid!sequence!might!affect!its!function.!
Students!might!suggest!that!since!the!four!missense!mutations!in!the!Mc1r!gene!change!the!amino!acid!
sequence!of!the!MC1R !protein,!the!protein!will!not!function!properly,!as!a!protein’s!function!is!determined!by!
its!struct u re .!
6.!Many!proteins,!including!MC1R,!contain!several!structural!domains!that!can!fold!and!function!inde pe nd en tly!
from!the!rest.!Th e!d omain!names!w ere !pro vide d !for!ea ch!p ortio n!o f!DN A !seq ue nc e!yo u !trans late d!ea rlier.!An sw e r!
the!following!questio ns. !
a.!Where!is!the!MC1R!protein!found,!and!what!is!its!function?!Be!specific.!
It!is!a!rece p tor !pro tein!e m be d de d!in!th e!m e m b ran e!o f!me lan oc ytes .!It!is!specialized !for!pig m en t!pro d uctio n.!
b.!Which!protein!domains!contain!the!four!Mc1r!missense!mutations?!(Refer!to!the!gene!tables!you!completed!
earlier.)!
The!mutation!at!018!is!in!Extracellular!Domain!I,!the!mutation!a t!1 0 9 !is!in !E x t ra c e llu la r!Domain!III,!th e !mutation!
at!160!is!in!Intracellular!Domain!I,!and!the!mutation!at!233!is!in!Intracellular!Domain!III.!
c.!Define!“extracellular.”!
Extracellular!means!“something!outside!of!a!cell.”!
d.!Define!“intracellular.”!
Intracellu la r !means!“something!in sid e !o f!a !c e ll.”!
e.!Why!is!it!significant!that!the!four!missense!mutations!are!found!in!the!extracellular!and!intracellular!domains!of!
the!protein?!Explain!yo ur!an sw er.!(H int:!Think!a bou t!M C1 R’s!fun ction .) !
Specific!answers!will!va r y,!b u t !st u d e n ts !sh o u ld !h a v e !th e !id e a !th a t !a !p ro t ein !t h a t!s p a n s!a !c e ll!membra n e !h as !a !
portion!that!projects!out!of!the!cell!(extracellular)!and!a!portion!that!projects!into!the!cell!(intracellular).!This!
type!of!recep tor!p rote in!u sua lly!functio ns!in!eithe r!cell!trans port!o r!cell!signaling .!Cha nge s!in!the!stru ctu re!of!
extracellular!and!intracellular!portions!can!change!the!function!of!the!protein!in!the!signaling!pathway!or!the!
transport!m ec ha nism .!(N ote :!See !the !lesson !“Th e!B ioch emistry!and!Cell!Signaling!Pathway!of!the!Mc1r!Gene”!
for!more!deta il!on!this!con cep t.)!!
! ! !
!
www.BioInteractive.org! !
LESSON!
TEACHER!MATERIALS!
The Making of the Fittest:
Natural Selection and Adaptation
Educator Materials!
Lesson
The Making of the Fittest
Natural Selection and Adaptation
!
!!!!!!!!!!!
Published*February,*2017*
**********************************Page*8*of*8
!
7.!Using!the!information!on!the!Mc1r!gene!in!the!introduction!and!your!knowledge!of!proteins,!develop!a!
hypothesis!to!explain!how!the!change!in!MC1R!protein!function!might!directly!affect!a!rock!pocket!mouse’s!coat!
color.!Be!specific!and!consider!both!the!light-colored!and!dark-colored!phenotypes.!
Specific!answers!will!vary,!but!students!should!suggest!that!the!normal!MC1R!receptor!protein!will!produce!
relative!amounts!of!eum elanin!and!pheomelanin!that!will!result!in!the!light!coat!color.!In!addition,!the!dark-
colored!mouse!population!contains!the!mutant!Mc1r!gene,!which!results!in!a!different!receptor!protein.!This!
change!in!structure!might!lead!to!increased!production!of!eumelanin,!which!results!in!the!dark!color.!
8.!Explain!why!the!mutation!at!amino!acid!location!211!is!not!as!significant!as!the!other!four!mutations.!
It!is!a!silent!mutation,!so!the!amino!acid!in!that!position!does!not!change,!nor!does!the!structure!of!the!specific!
domain.!This!is!important!because!a!protein’s!structure!relates!to!its!function.!No!change!in!the!structure!
suggests!that!there!is!no!change!in!the!function!of!this!particular!domain!of!the!protein.!
9.!Mutations!are!a!source!of!genetic!variation.!In!the!film,!Dr.!Sean!Carroll!says!that!mutations!occur!randomly.!
What!does!this!mean?!
Sample!answer:!“It!means!that!mutations!do!not!occur!for!a!purpose!or!for!any!predetermined!result.”!!
10.!It!is!a!com mon!misco n c ep t io n!t h a t!“ a ll!m u t at io n s!a re !b a d .” !U se !t he !exam ple!of!rock!pocket!mice!to!explain!
why!this!statement!is!not!true.!In!your!answer,!explain!how!the!dark!coat-color!mutation!can!be!an!advantage!to!
some!mice!and!a!disadvantage!to!others.!
Sample!answer:!“Mutations!can!result!in!new!traits.!The!selective!advantage!provided!by!a!trait!depends!on!the!
environment.!For!example,!on!a!light!substrate,!individuals!with!dark-colored!coats!would!be!at!a!disadvantage!
because!they!would!stand!out!more!than!individuals!with!light-colored!coats,!making!them!easier!for!predators!
to!spot.!How ev er,!in!the !da rk!lav a!flow !ha bita t,!those !sam e !da rk-colored!individuals!would!have!a!selective!
advantage!because!they!would!be!better!camouflaged!than!light-colored!individuals.!So!the!statement!that!“all!
mutations!are!bad”!is!incorrect,!because!there!are!different!selective!pressures!on!the!traits!produced!by!
mutations!depending!on!the!habitat.!There!are!also!silent!mutations!that!do!not!change!the!resulting!protein;!
these!are!ne utra l,!neithe r!go od !no r!ba d.”!
11.!Use!your!understanding!of!evolution!and!the!information!in!the!film!to!explain!how!the!dark-colored!mutation!
came!to!be!so!common!in!som e!populations!of!rock!pocket!mice.!Be!specific.!
Sample!answer:!“The!dark-colored!mouse!has!a!selective!advantage!in!a!hab it a t!s u ch !a s !th e !P inacate!lava!flow,!
which!has!a!dark-colored!substrate.!Since!rock!pocket!mice!reproduce!quickly!and!often,!the!frequency!of!this!
favored!trait!wo uld!sp rea d!rap idly!throu gh !the!po pu lation.!A ny!light-colored!mice!in!the!dark-colored!habitat!
would!be!at!a!selective!disadvantage,!thus!de cre asin g!the ir!ge ne !freq ue nc y!in!futu re!g en era tion s.!In!this!w ay,!
favorable!traits!accu m u late!an d!incre ase !in!frequ enc y—just!as!Cha rle s!D a rwin!explaine d.”!
!
AUTHOR!
Ann%Brokaw%%
AP%Biology%Teacher%
Rocky%River%High%School%%
Rocky%River,%Ohio%
%
