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Level 2 Biology, 201491159 Demonstrate understanding of gene expression

9.30 am Monday 17 November 2014 Credits: Four

Achievement Achievement with Merit Achievement with ExcellenceDemonstrate understanding of gene expression.

Demonstrate in-depth understanding of gene expression.

Demonstrate comprehensive understanding of gene expression.

Check that the National Student Number (NSN) on your admission slip is the same as the number at the top of this page.

You should attempt ALL the questions in this booklet.

If you need more space for any answer, use the page(s) provided at the back of this booklet and clearly number the question.

Check that this booklet has pages 2 – 12 in the correct order and that none of these pages is blank.

YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.

QUESTION ONE: MAKING PROTEINS

(a) The diagram below shows the cell process, transcription.

Onthediagram,fillinthemissingbasesonthemRNAstrand.

T

T

C

C

A

A

C

T

T

T

T

TT

TT

C

C

C

C

C

C

C

C

A

A

A

A

A

A

A

A

A

A

AT

C

G

G

G

G

G

G

G

G

G

G

G

G

G

G

GG

CC

T

DNA molecule

mRNA

Adaptedfromhttp://www.scientificpsychic.com/fitness/aminoacids1.html

(b) Proteinsynthesisinvolvestwostages:transcriptionandtranslation.

Compareandcontrastthesetwocellprocessesandtheirroleinproteinsynthesis.

Inyouranswer:

• explainthepurposeandprocessesoftranscriptionANDtranslation

• discussthesimilaritiesanddifferencesbetweentranscriptionandtranslation.

You may use diagrams to support your answer.

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There is more space for your answer to this question on the following page.

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This page has been deliberately left blank.

The examination continues on the following page.

QUESTION TWO: COAT COLOUR

Gene A Gene B

Tyrosinase enzyme Enzyme for expression

Tyrosine Melanin Coat colour

Tyrosine Metabolic Pathway

http://en.wikipedia.org/wiki/Siamese_(cat)

Skinandhaircolouringareinfluencedbythepigmentmelanin.Melaninisaproteinthatismadeviathetyrosinepathway,andtherearetwogenesinvolvedinthepathway,whichleadtoitsexpression.

Albinoanimalslackthepigmentmelanin,andsohavenocolouringoftheirskin,hair,andeyes.Siamesecats,liketheoneinthepictureabove,showaformofalbinism.However,Siamesecatspossessamutatedgenethatcodesfortheenzymetyrosinase,whichisanenzymeinthemelaninexpressionpathway.Thisenzymeistemperaturesensitive,andsoSiamesecatscanproducethepigmentmelanininbodyextremities,suchasthefeet,tail,andface,whichgivesthemdarkercolouring.

DiscusshowthemetabolicpathwayformelaninandtheenvironmentinteracttoinfluencethecoatcolourinSiamesecats.

Inyouranswer:

• describewhatametabolicpathwayis

• explainwhySiamesecatshavedarkercolourationaroundtheirbodyextremitiessuchasthenose,feetandtail,andnotaroundtheirchestarea

• usingthediagramabove,discusshowgenesandenzymescontrolthemetabolicpathwayformelanin,andhowthiscausesSiamesecatstobealbino.

For copyright reasons, this resource cannot be

reproduced here.

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QUESTION THREE: THE GENETIC CODE

mRNA (codon) : Amino Acid Table

Second PositionU C A G

Firs

t Pos

ition

UUUU PheUUC PheUUA LeuUUG Leu

UCU SerUCC SerUCA SerUCG Ser

UAU TyrUAC TyrUAA STOPUAG STOP

UGU CysUGC CysUGA STOPUGG Trp

UCAG

Third Position

CCUU LeuCUC LeuCUA LeuCUG Leu

CCU ProCCC ProCCA ProCCG Pro

CAU HisCAC HisCAA GlnCAG Gln

CGU ArgCGC ArgCGA ArgCGG Arg

UCAG

AAUU IleAUC IleAUA IleAUG Met

ACU ThrACC ThrACA ThrACG Thr

AAU AsnAAC AsnAAA LysAAG Lys

AGU SerAGC SerAGA ArgAGG Arg

UCAG

GGUU ValGUC ValGUA ValGUG Val

GCU AlaGCC AlaGCA AlaGCG Ala

GAU AspGAC AspGAA GluGAG Glu

GGU GlyGGC GlyGGA GlyGGG Gly

UCAG

TraceyGreenwood,RichardAllan,Year 12 Biology 2003,(Hamilton:Biozone,2003),p287.

(a) ThemRNAcodonsequenceforpartofanormalhaemoglobinproteinisshowninthetablebelow.

• CompletethenormaltemplateDNAsequenceinthetablebelow.

• CompletethenormalaminoacidsequenceusingthemRNA:AminoAcidtableabove

Normal template DNA

Normal mRNA AUG GUG CAC CUG ACU CCU GAG UUG

Normal amino acid

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Sicklecelldisease(previouslyknownassicklecellanaemia)isaninheriteddisordercausedbyamutationonthehaemoglobin(redbloodcell)gene.The20thnucleotideintheDNAsequence,hasaTnucleotidesubstitutedwithanAnucleotidebaseontheDNAstrand.

(b) Usingthetablebelow,describethemutatedaminoacidsequenceresultingfromTbeingreplacedatthe20thnucleotideposition.

Mutated DNA– – – – – – – – – – – – – – – – – – – – – – –

Mutated mRNA

Mutated amino acid

(c) Discusswhathappenstothefinalproteinasaresultofthismutation.

Inyouranswer:

• explainhowthesubstitutionmutationaffectsthesequenceofbasesandthefinalprotein

• discusswhatwouldhappentotheDNAbasesequenceandfinalproteinifanadditionalnucleotidewasinsertedintothesequenceasanextra,ratherthanbeingsubstitutedforanother, and

• linkthistothedegeneracyofthegeneticcode.

There is more space for your answer to this question on the following page.

20th nucleotide

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QUESTION NUMBER

Extra paper if required.Write the question number(s) if applicable.

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QUESTION NUMBER

Extra paper if required.Write the question number(s) if applicable.