Unit B7 - 8: Cell Biology Unit B7 - 8: Cell Biology (Protein Synthesis)(Protein Synthesis)

Authored by Michelle ChomaAuthored by Michelle Choma©©

Students who have fully met the prescribed learning outcomes Students who have fully met the prescribed learning outcomes (PLO’s) are able to:(PLO’s) are able to:

B7. Demonstrate an understanding of B7. Demonstrate an understanding of the process of protein synthesis. the process of protein synthesis. identify the roles of DNA, mRNA, tRNA, identify the roles of DNA, mRNA, tRNA,

and ribosomes in the process of and ribosomes in the process of transcription and translation, including transcription and translation, including initiation, elongation, and termination.initiation, elongation, and termination.

Unit B7 ContinuedUnit B7 Continued

determine the sequence of amino acids determine the sequence of amino acids coded for by a specific DNA sequence coded for by a specific DNA sequence (genetic code), given a table of mRNA (genetic code), given a table of mRNA codons.codons.

identify the complementary nature of identify the complementary nature of the mRNA codon and the tRNA anti-the mRNA codon and the tRNA anti-codon.codon.

B8. Explain how mutations in B8. Explain how mutations in DNA affect protein synthesis.DNA affect protein synthesis. give examples of two environmental give examples of two environmental

mutagens that can cause mutations in mutagens that can cause mutations in humans.humans.

use examples to explain how mutations use examples to explain how mutations in DNA change the sequence of amino in DNA change the sequence of amino acids in a polypeptide chain, and as a acids in a polypeptide chain, and as a result may lead to genetic disorders.result may lead to genetic disorders.

Web Sites & Links for Web Sites & Links for Protein Synthesis Protein Synthesis

http://www.coolschool.ca/lor/BI12/unit6/U06L00.hthttp://www.coolschool.ca/lor/BI12/unit6/U06L00.htmm (Unit 06) (Unit 06)

☺☺Scroll to Scroll to Lesson 01 – Lesson 04Lesson 01 – Lesson 04 (‘U06L01 – L04’) (‘U06L01 – L04’) http://highered.mcgraw-hill.com/sites/http://highered.mcgraw-hill.com/sites/

0072421975/student_view0/chapter24/ 0072421975/student_view0/chapter24/ (Mader’s Student Edition Website Support for Chapter (Mader’s Student Edition Website Support for Chapter

24; Animations, quizzes, flashcards, Thinking 24; Animations, quizzes, flashcards, Thinking Scientifically etc.)Scientifically etc.)

http://sps.k12.ar.us/massengale/pwpt_biology.htmhttp://sps.k12.ar.us/massengale/pwpt_biology.htm Power point presentation on Protein Synthesis Power point presentation on Protein Synthesis

http://sps.k12.ar.us/massengale/http://sps.k12.ar.us/massengale/nucleic_acids_.htm nucleic_acids_.htm

(Nucleic acids & protein synthesis, animations)(Nucleic acids & protein synthesis, animations)

Some more….Some more…. http://http://

www.phschool.com/science/biology_place/index.hwww.phschool.com/science/biology_place/index.htmltml

Check out the ‘Check out the ‘The Biology PlaceThe Biology Place’; Click on link to ’; Click on link to ‘BioCoach’ activities on Transcription & Translation. ‘BioCoach’ activities on Transcription & Translation.

Fabulous Reviews, Animations, Practice & Self-quiz etc. Fabulous Reviews, Animations, Practice & Self-quiz etc. http://www.scilinks.org/retrieve.asp http://www.scilinks.org/retrieve.asp

(Sign up on this site. Great links on protein synthesis: (Sign up on this site. Great links on protein synthesis: Link code, cbn-4123) Link code, cbn-4123)

http://www.phschool.com/webcodes10/index.cfm?http://www.phschool.com/webcodes10/index.cfm?wcprefix=cbe&wcsuffix=4123&fuseaction=home.wcprefix=cbe&wcsuffix=4123&fuseaction=home.gotoWebCode&x=11&y=18 gotoWebCode&x=11&y=18

(Great animation on protein synthesis) (Great animation on protein synthesis)

And some more….And some more…. http://http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.htmlwww.pbs.org/wgbh/aso/tryit/dna/shockwave.html http://www.pbs.org/wgbh/aso/tryit/dna/index.html# http://www.pbs.org/wgbh/aso/tryit/dna/index.html# (Protein Synthesis activity & animation)(Protein Synthesis activity & animation) http://nobelprize.org/educational_games/medicine/dna/http://nobelprize.org/educational_games/medicine/dna/

intro.html (Review & Animations of protein synthesis)intro.html (Review & Animations of protein synthesis) http://www.wisc-online.com/objects/index_tj.asp?http://www.wisc-online.com/objects/index_tj.asp?

objid=AP1302 objid=AP1302 http://www.eurekacityschools.org/ehs/riggsw/http://www.eurekacityschools.org/ehs/riggsw/

Transcription.pptTranscription.ppt (Powerpoint) (Powerpoint) http://learn.genetics.utah.edu/ (Animation) http://learn.genetics.utah.edu/ (Animation)

Terrific activities. Check out the Genetics Reference Series Terrific activities. Check out the Genetics Reference Series

and click on link to ‘The Basics and Beyond’. Follow and click on link to ‘The Basics and Beyond’. Follow directions for Transcribing & Translating a Gene.directions for Transcribing & Translating a Gene.

And more!And more!

http://http://www.pbs.org/wgbh/aso/tryit/dna/shocwww.pbs.org/wgbh/aso/tryit/dna/shockwave.htmlkwave.html

www.lewport.wnyric.org/www.lewport.wnyric.org/jwanamaker/animations/Proteinjwanamaker/animations/Protein%20Synthesis%20-%20long.html%20Synthesis%20-%20long.html

http://www.wisc-online.com/objects/http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302index_tj.asp?objid=AP1302

And more linksAnd more links http://waynesword.palomar.edu/lmexer3.htmhttp://waynesword.palomar.edu/lmexer3.htm ☺☺Check out the many topics & related articles in the ‘Table Check out the many topics & related articles in the ‘Table

of Contents’ of Contents’ http://www.estrellamountain.edu/faculty/farabee/biobk/http://www.estrellamountain.edu/faculty/farabee/biobk/

BioBookPROTSYn.htmlBioBookPROTSYn.html http://distance.stcc.edu/BIOL102/Lectures/lesson10/http://distance.stcc.edu/BIOL102/Lectures/lesson10/

makeprot.htmmakeprot.htm http://www.emc.maricopa.edu/faculty/farabee/BIOBK/http://www.emc.maricopa.edu/faculty/farabee/BIOBK/

BioBookglossN.html#nucleic acidsBioBookglossN.html#nucleic acids http://workbench.concord.org/web_content/unitV/http://workbench.concord.org/web_content/unitV/

sickle_cell_worksheet_s.html (a model-based activity to sickle_cell_worksheet_s.html (a model-based activity to make a sickle-cell mutation)make a sickle-cell mutation)

http://workbench.concord.org/web_content/unitV/http://workbench.concord.org/web_content/unitV/muta_wksht_s.html (a model-based activity to make muta_wksht_s.html (a model-based activity to make substitution & deletion mutations)substitution & deletion mutations)

http://www.quizmebc.ca/http://www.quizmebc.ca/

IntroductionIntroduction

Protein synthesis is the Protein synthesis is the manufacture/synthesis of proteins.manufacture/synthesis of proteins.

Occurs in the Occurs in the nucleusnucleus and and cytoplasmcytoplasm..

The genetic codes for specific proteins are The genetic codes for specific proteins are located on the DNA, e.g. codes for keratin, located on the DNA, e.g. codes for keratin, collagen, Hb, polymercollagen, Hb, polymerasease, amyl, amylasease, pepsin , pepsin etc.etc.

Introduction ContinuedIntroduction Continued

The The triplet genetic codestriplet genetic codes on DNA are on DNA are called called codonscodons. This is a sequence of . This is a sequence of threethree DNA bases. DNA bases.

The site for protein synthesis occurs The site for protein synthesis occurs on the on the ribosomesribosomes (rRNA and protein) (rRNA and protein) in the cytoplasm.in the cytoplasm.

Protein synthesis: Protein synthesis: divided into 2 processes:divided into 2 processes:

(A) (A) TranscriptionTranscription:: copying the copying the codons for a protein from a segment codons for a protein from a segment of the DNA strand to make mRNA of the DNA strand to make mRNA (messenger RNA); requires 2 enzymes (messenger RNA); requires 2 enzymes ((helichelicasease, RNA polymer, RNA polymerasease). ).

Includes steps of Includes steps of initiationinitiation, , elongationelongation and and terminationtermination. .

Second ProcessSecond Process

(B)(B) TranslationTranslation:: translate the translate the sequence of codons for the protein sequence of codons for the protein on the mRNA to build a protein at the on the mRNA to build a protein at the ribosome; tRNA assists in this ribosome; tRNA assists in this process. process.

Includes steps of Includes steps of initiationinitiation, , elongationelongation and and terminationtermination..

B7– Roles of the Molecules B7– Roles of the Molecules Involved in Protein Involved in Protein

SynthesisSynthesis(a) DNA(a) DNA Contains the information/Contains the information/genetic genetic

codecode//triplet codestriplet codes//codonscodons for the for the synthesis of proteins, e.g. synthesis of proteins, e.g. TCG, ATG, TCG, ATG, ATT.ATT.

Provides a Provides a templatetemplate for mRNA to be for mRNA to be produced.produced.

Let’s draw this together!!Let’s draw this together!!

(b) mRNA(b) mRNA Carries the coded message from the Carries the coded message from the

nucleus to the cytoplasm, e.g. codons nucleus to the cytoplasm, e.g. codons UAA, CGC, AGUUAA, CGC, AGU

Sets the order of amino acids for Sets the order of amino acids for protein synthesis by the sequence of protein synthesis by the sequence of codonscodons. (. (CodonCodon = 3 bases/ = 3 bases/ nucleotides in a DNA or RNA sequence nucleotides in a DNA or RNA sequence which specify a single amino acid.)which specify a single amino acid.)

(c) Ribosomes(c) Ribosomes Provides a site for mRNA and tRNA to Provides a site for mRNA and tRNA to

join together by complementary base join together by complementary base pairing.pairing.

Site for protein synthesis (i.e. Site for protein synthesis (i.e. translation) where it translates mRNA translation) where it translates mRNA and allows amino acids to bond and allows amino acids to bond (peptide bond).(peptide bond).

Note: Note:

rRNA & proteinrRNA & protein make up themake up the small small andand large subunitslarge subunits of ribosomesof ribosomes.. The small subunit contains the The small subunit contains the binding site for mRNA and the large binding site for mRNA and the large subunit contains 2 binding sites for subunit contains 2 binding sites for tRNA ~ amino acid and a tRNA ~ amino acid and a dehydration synthesis site!dehydration synthesis site!

Remember this!!??Remember this!!??

(d) tRNA(d) tRNA Carries the Carries the

specific amino specific amino acid to the acid to the ribosome where ribosome where its its anticodonanticodon complementary complementary base pairs with base pairs with the mRNA codon, the mRNA codon, e.g. mRNA codon- e.g. mRNA codon- UUAUUA; anticodon- ; anticodon- AAUAAU..

(e) Amino acids(e) Amino acids These are the monomers of proteins These are the monomers of proteins

and are picked up by tRNA in the and are picked up by tRNA in the cytoplasm, i.e. tRNA~ amino acids.cytoplasm, i.e. tRNA~ amino acids.

Note:Note:

mRNA Codon TablemRNA Codon Table (see below) tells (see below) tells what 3 bases on mRNA code for each what 3 bases on mRNA code for each amino acid (64 combinations of 3 bases) amino acid (64 combinations of 3 bases)

Methionine (AUG)Methionine (AUG) on mRNA is called the on mRNA is called the ‘START codon’ because it triggers the ‘START codon’ because it triggers the linking of amino acids linking of amino acids

UAA, UGA, & UAGUAA, UGA, & UAG on mRNA signal on mRNA signal ribosomes ribosomes to stop linking amino acids to stop linking amino acids togethertogether

DNACodon

mRNACodon

tRNAAnticodon

AminoAcid

  GCU    

TAC      

    AUU  

  UUU    

TCA      

    UCU  

CTT      

B7– Steps of Protein B7– Steps of Protein SynthesisSynthesis

Key words:Key words: initiation, elongation, initiation, elongation, termination, transcription, termination, transcription, translation, elongation, DNA, mRNA, translation, elongation, DNA, mRNA, tRNA, ribosome, amino acid, triplet tRNA, ribosome, amino acid, triplet code/codons, template, H-bonds, code/codons, template, H-bonds, complementary pairing, RNA complementary pairing, RNA polymerase, anticodon, peptide polymerase, anticodon, peptide bond, polypeptides, dehydration bond, polypeptides, dehydration synthesis. synthesis.

AnimationsAnimations

http://highered.mcgraw-hill.com/sites/0072421975/http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter24/animations__english_.htmlstudent_view0/chapter24/animations__english_.html

http://www.pbs.org/wgbh/aso/tryit/dna/index.html# http://www.pbs.org/wgbh/aso/tryit/dna/index.html# (Protein Synthesis activity & animation)(Protein Synthesis activity & animation) http://www.lewport.wnyric.org/jwanamaker/http://www.lewport.wnyric.org/jwanamaker/

animations/Protein%20Synthesis%20-%20long.html animations/Protein%20Synthesis%20-%20long.html http://www.wisc-online.com/objects/index_tj.asp?http://www.wisc-online.com/objects/index_tj.asp?

objid=AP1302objid=AP1302 http://learn.genetics.utah.edu/ http://learn.genetics.utah.edu/ http://www.eurekacityschools.org/ehs/riggsw/http://www.eurekacityschools.org/ehs/riggsw/

Transcription.ppt Transcription.ppt

1.1. TranscriptionTranscription

(involves steps of (involves steps of initiation, initiation, elongation & terminationelongation & termination))

Location: nucleusLocation: nucleus Product: mRNAProduct: mRNA

Requires 2 enzymes: Requires 2 enzymes: helichelicasease and and RNA polymerRNA polymerasease..

Here we go…..Here we go…..

(a) DNA containing genetic code for (a) DNA containing genetic code for protein is in triplet codes.protein is in triplet codes.

(b) (b) InitiationInitiation: RNA polymerase : RNA polymerase initiatesinitiates transcription by locating and binding transcription by locating and binding to the beginning of a gene/code (i.e. to the beginning of a gene/code (i.e. the the promoter promoter regionregion))..

(c) (c) ElongationElongation: -: -HelicHelicasease unwinds, unzips unwinds, unzips DNA, breaks H-bonds and provides a DNA, breaks H-bonds and provides a template for mRNA formation.template for mRNA formation.

RNA polymeraseRNA polymerase travels down the travels down the template and complementary base pairs template and complementary base pairs RNA nucleotides with DNA codons forming RNA nucleotides with DNA codons forming a mRNA,a mRNA, e.g. DNA – CAT; mRNA – GUA.e.g. DNA – CAT; mRNA – GUA.

RNA polymerRNA polymerasease joins adjacent joins adjacent

nucleotides to mRNA, forming the S-P-S nucleotides to mRNA, forming the S-P-S backbone.backbone.

(d) (d) TerminationTermination: -RNA polymerase : -RNA polymerase reaches reaches termination termination sequence at end sequence at end of gene/code and STOPS mRNA of gene/code and STOPS mRNA synthesis. RNA polymerase releases synthesis. RNA polymerase releases the mRNA and detaches from the the mRNA and detaches from the DNA. DNA.

mRNA exits nucleus through its pores mRNA exits nucleus through its pores and enters the cytoplasm; DNA and enters the cytoplasm; DNA rejoins.rejoins.

Note:Note:

mRNA carries a sequence of codons mRNA carries a sequence of codons (linear order of three RNA bases (linear order of three RNA bases complementary to DNA triplet code) complementary to DNA triplet code) to the ribosome…to the ribosome…

One is a “STOP” codon, e.g. UAA, One is a “STOP” codon, e.g. UAA, UAG and UGA and a “START” codon, UAG and UGA and a “START” codon, e.g. AUG (Methionine).e.g. AUG (Methionine).

2. Translation2. Translation (involves steps of (involves steps of initiationinitiation, , elongationelongation and and terminationtermination))

Location: cytoplasm at the ribosomeLocation: cytoplasm at the ribosome Product: protein/polypeptideProduct: protein/polypeptide

TranslationTranslation

(a) tRNAs in the cytoplasm attach the (a) tRNAs in the cytoplasm attach the correct amino acid to one end (aided by correct amino acid to one end (aided by enzymes). enzymes).

(b) (b) InitiationInitiation: tRNA~methionine binds to : tRNA~methionine binds to small subunit and this binds to the mRNA. small subunit and this binds to the mRNA. tRNA anticodon (UAC) complementary tRNA anticodon (UAC) complementary pairs with mRNA “ START” codon (AUG). pairs with mRNA “ START” codon (AUG). Large subunit binds to the small subunit Large subunit binds to the small subunit assembling a ribosome.assembling a ribosome.

Translation continuedTranslation continued

(c) (c) ElongationElongation: -Another tRNA (i.e. : -Another tRNA (i.e. tRNA~amino acid) with its anticodon tRNA~amino acid) with its anticodon complementary base pairs with mRNA complementary base pairs with mRNA codon on the ribosome. (It has codon on the ribosome. (It has 2 2 binding sites for incoming tRNA~aa)binding sites for incoming tRNA~aa)

Ribosomes move along one codon toRibosomes move along one codon to

receive the next incoming tRNA~aa.receive the next incoming tRNA~aa.

Amino acid undergoes dehydration Amino acid undergoes dehydration synthesis and forms a peptide bond.synthesis and forms a peptide bond.

““Empty” or outgoing tRNA will bond Empty” or outgoing tRNA will bond with another amino acid in the with another amino acid in the cytoplasm, i.e. tRNA~aa.cytoplasm, i.e. tRNA~aa.

(d) (d) TerminationTermination: Synthesis of : Synthesis of polypeptide until a “STOP” codon on polypeptide until a “STOP” codon on mRNA (UAA, UAG, UGA). mRNA (UAA, UAG, UGA).

Termination of protein synthesis and Termination of protein synthesis and the polypeptide chain and mRNA are the polypeptide chain and mRNA are released from the ribosome. released from the ribosome.

Ribosome subunits separate.Ribosome subunits separate.

Ribosomes can synthesize 5-15 Ribosomes can synthesize 5-15 peptide bonds/sec!peptide bonds/sec!

Most proteins are 100-200 aa long & Most proteins are 100-200 aa long & takes less than a minute to be takes less than a minute to be synthesized!synthesized!

http://nobelprize.org/educational_games/http://nobelprize.org/educational_games/medicine/dna/b/translation/medicine/dna/b/translation/translation.html (click on animation icon)translation.html (click on animation icon)

http://highered.mcgraw-hill.com/olcweb/http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis (Great micro06.swf::Protein%20Synthesis (Great animation)animation)

http://sps.k12.ar.us/massengale/http://sps.k12.ar.us/massengale/proteinsynthesis%20ppt.ppt (Nice power proteinsynthesis%20ppt.ppt (Nice power points 1 & 2 on Transcrip/lation)points 1 & 2 on Transcrip/lation)

http://sps.k12.ar.us/massengale/proteinhttp://sps.k12.ar.us/massengale/protein%20synthesis2%20ppt.ppt %20synthesis2%20ppt.ppt

B7– Problems Using the B7– Problems Using the “Table of mRNA codons”“Table of mRNA codons”

Use the following table to answer Use the following table to answer questions 1 – 7.questions 1 – 7.

Note: most of the amino acids are Note: most of the amino acids are coded with 2, 3 or even 4 different coded with 2, 3 or even 4 different codons. Of these 64 codons. Of these 64 codonscodons, 61 are , 61 are used to program the 20 amino acids. used to program the 20 amino acids. Three of the 64 codons are used as Three of the 64 codons are used as signals to start or stop the program. signals to start or stop the program.

LinksLinks

http://learn.genetics.utah.edu/ Visit http://learn.genetics.utah.edu/ Visit the Genetics Reference Series and the Genetics Reference Series and click on link to ‘The Basics and click on link to ‘The Basics and Beyond’. Follow the directions for Beyond’. Follow the directions for synthesis of a protein.synthesis of a protein.

Ok Let’s Try it Out!Ok Let’s Try it Out!

1.) 1.) What are the RNA triplet codes for What are the RNA triplet codes for Lysine? Leucine?Lysine? Leucine?

using the mRNA table, the codons for using the mRNA table, the codons for Lysine are AAA or AAG.Lysine are AAA or AAG.

using the mRNA table, the codons for using the mRNA table, the codons for Leucine are CUU, CUC, CUA, CUG, Leucine are CUU, CUC, CUA, CUG, UUA and UUG. UUA and UUG.

2.) 2.) What is the DNA triplet code for What is the DNA triplet code for Tryptophan?Tryptophan?

mRNA = UGG (from table)mRNA = UGG (from table)

DNA = ACC.DNA = ACC. 3.) 3.) What are the mRNA triplet codons What are the mRNA triplet codons

for “STOP”?for “STOP”?

using the mRNA table, the using the mRNA table, the codons codons are UAA, UAG and UGA.are UAA, UAG and UGA.

4.) 4.) The The anticodonanticodon on a tRNA is GCU. on a tRNA is GCU. Determine the name of the amino Determine the name of the amino acid and its triplet codon.acid and its triplet codon.

tRNA anticodon GCU would tRNA anticodon GCU would complementary base pair with mRNA complementary base pair with mRNA CGA at the ribosome.CGA at the ribosome.

using the table, the amino acid code using the table, the amino acid code for CGA is Arginine.for CGA is Arginine.

5.) 5.) DNA contains the following genetic DNA contains the following genetic code: code: TACAAGATTTACAAGATT. Determine the . Determine the amino acid sequence.amino acid sequence.

DNA = TAC|AAG|ATT DNA = TAC|AAG|ATT

mRNA = AUG|UUC|UAAmRNA = AUG|UUC|UAA

= methionine= methionine--phenylalaninephenylalanine--stop stop

(from table).(from table).

B8 – Environmental B8 – Environmental Mutagens Causing Mutagens Causing

MutationsMutations UV radiation, X-rays, gamma rays.UV radiation, X-rays, gamma rays. Industrial chemicals, e.g. PCB’s, pollutants, Industrial chemicals, e.g. PCB’s, pollutants,

pesticides, and food additives, i.e. pesticides, and food additives, i.e. carcinogenscarcinogens

Heavy metals such as Lead (Pb), Mercury Heavy metals such as Lead (Pb), Mercury (Hg).(Hg).

Viruses can cause mutations by adding or Viruses can cause mutations by adding or deleting a nucleotide or by adding a new deleting a nucleotide or by adding a new section of DNA from another organism; section of DNA from another organism; (viruses change a proto-oncogene (normal (viruses change a proto-oncogene (normal gene) into an oncogene (cancer-causing gene) into an oncogene (cancer-causing gene), e.g. HIV.gene), e.g. HIV.

B8 – DNA Mutations B8 – DNA Mutations Affecting Protein Synthesis Affecting Protein Synthesis

and Possible Genetic and Possible Genetic DisordersDisorders

Altering the codeAltering the code for the synthesis of for the synthesis of proteins, may result in proteins, may result in different codonsdifferent codons combining combining different amino acidsdifferent amino acids with with different protein shapesdifferent protein shapes andand therefore therefore function is impairedfunction is impaired (e.g. (e.g. Sickle-cell anemiaSickle-cell anemia causing sickle-causing sickle-

shaped RBC’s, cystic fibrosis, muscular shaped RBC’s, cystic fibrosis, muscular dystrophy and other diseases/disorders). dystrophy and other diseases/disorders).

Also, if the protein is an enzyme, Also, if the protein is an enzyme, E + SE + S (enzyme + substrate) (enzyme + substrate) reactionreaction may not may not occur or if the protein is a membrane occur or if the protein is a membrane protein, the protein, the cell membranecell membrane will not will not function properly. function properly.

Three types of gene/DNA Three types of gene/DNA Mutations:Mutations:

DeletionDeletion

AdditionAddition

SubstitutionSubstitution

1.)1.) DeletionDeletion

One or more nucleotides are deleted.One or more nucleotides are deleted.

This alters the code and therefore This alters the code and therefore alters the polypeptide and its alters the polypeptide and its function for the cell.function for the cell. E.g. Deletion of N-base, Cytosine from E.g. Deletion of N-base, Cytosine from

codon:codon: Normal DNA: TAC|GGG|ATG|TCA|Normal DNA: TAC|GGG|ATG|TCA| Mutation:Mutation: TATACCG|GGA|TGT|CAG|GGA|TGT|CA

2.)2.) AdditionAddition

One or more nucleotides are added.One or more nucleotides are added.

This pushes all bases back one code This pushes all bases back one code and therefore alters the polypeptide and therefore alters the polypeptide and its function for the cell.and its function for the cell. E.g. Addition of an Adenine base to E.g. Addition of an Adenine base to

codon:codon:

Normal DNA:Normal DNA: TAC|GGG|ATG|TCA|TAC|GGG|ATG|TCA| Mutation:Mutation: AATA|CGG|GAT|GTC|ATA|CGG|GAT|GTC|A

3.)3.) SubstitutionSubstitution

Involves a change in a single Involves a change in a single nucleotide and a change in a specific nucleotide and a change in a specific codon.codon.

When substituting a base the results When substituting a base the results are variable.are variable. E.g.1:E.g.1: CC substituting for U: substituting for U:

Normal RNA:Normal RNA: UAU = Tyrosine.UAU = Tyrosine. Substitute:Substitute: UA UACC = Tyrosine. = Tyrosine. No noticeable effectNo noticeable effect on these codons on these codons

as they are both for tyrosine.as they are both for tyrosine.

E.g.2:E.g.2: GG substitute for C: substitute for C: Normal RNA:Normal RNA: UAC = Tyrosine.UAC = Tyrosine. Substitute:Substitute: UA UAGG = Stop. = Stop.

Drastic effectDrastic effect as UAG is a Stop codon as UAG is a Stop codon & the resulting protein may be too & the resulting protein may be too short and/or unable to function for short and/or unable to function for the cell.the cell.

E.g.3:E.g.3: Sickle-cell anemiaSickle-cell anemia Single base substitution Single base substitution

mutationmutation.. Mutation and triplet code for one Mutation and triplet code for one

amino acid is altered. Glutamate amino acid is altered. Glutamate ((CTTCTT or or CTCCTC) is changed to Valine ) is changed to Valine (CAT, CAG, CAA, or CAC).(CAT, CAG, CAA, or CAC).

Normal DNA:Normal DNA: ......GGA|......GGA|CTTCTT mRNA:mRNA: ......CCU|GAA......CCU|GAA Amino acid …..Amino acid …..--ProlineProline--

GlutamateGlutamate..Substituting Substituting AA for T. for T.

Normal DNA:Normal DNA: .......GGA| .......GGA|CTTCTT Mutated DNA: ......GGA|CMutated DNA: ......GGA|CAATT mRNA:mRNA: .......CCU|G .......CCU|GUUAA Amino acid ……Amino acid ……--ProlineProline--Valine.Valine.

This alters ONE codon and changes This alters ONE codon and changes Glutamate to Valine. Their chemical Glutamate to Valine. Their chemical properties differ which causes red properties differ which causes red blood cells to become abnormally blood cells to become abnormally sickle-shaped, causing sickle-cell sickle-shaped, causing sickle-cell anemia.anemia.

B8 – Mutation Problems B8 – Mutation Problems Using the “Table of mRNA Using the “Table of mRNA

codons”codons” Use the mRNA table in B7 to answer the Use the mRNA table in B7 to answer the

following examples of mutation problems.following examples of mutation problems. 1.) 1.) The base sequence of a section of DNA isThe base sequence of a section of DNA is

A A G C C T G C A.A A G C C T G C A.

Which of the following represents mRNA Which of the following represents mRNA produced from this DNA after a mutation has produced from this DNA after a mutation has occurred?occurred?

a) TTC GGA CGT b) TTC GUU CGT a) TTC GGA CGT b) TTC GUU CGT

c) UUC GGA CGU d) UUC GGA CUU c) UUC GGA CGU d) UUC GGA CUU

2.) 2.) The DNA strand The DNA strand C G A T G C G A C A T C G A T G C G A C A T T T undergoes a mutation in which the section undergoes a mutation in which the section coding for the amino acid threonine is lost. coding for the amino acid threonine is lost. Which of the following would be the correct Which of the following would be the correct codons after this mutation?codons after this mutation?using the table, the codons for threonine are using the table, the codons for threonine are __________, __________, ___________, __________, __________, ___________, ___________.___________.DNA sequence is CGA DNA sequence is CGA /______/______/______ /______/______/______

mRNA sequence is mRNA sequence is ______/______/______/______ . ______/______/______/______ . Now DELETE threonine from the mRNA. Now DELETE threonine from the mRNA. Therefore, the correct sequence of codons is Therefore, the correct sequence of codons is a. ACG/ CUG/ UAA b. GCU/ ACG/ CUG a. ACG/ CUG/ UAA b. GCU/ ACG/ CUG c. GCU/ CUG/ UAA d. GCU/ ACG/ UAA c. GCU/ CUG/ UAA d. GCU/ ACG/ UAA

3.)3.) The following is a DNA base sequence: The following is a DNA base sequence: GCA CCT ATA GGA ACCGCA CCT ATA GGA ACC

Explain any three things that would occur during Explain any three things that would occur during thethe translation translation of this gene if of this gene if ATA ATA underwent a underwent a mutation and was converted to mutation and was converted to A T TA T T . .

DNA DNA GCA CCT ATA GGA ACCGCA CCT ATA GGA ACCMutated DNA Mutated DNA GCA CCT ATT GGA ACCGCA CCT ATT GGA ACCmRNA _____ _____ _____ _____ _____mRNA _____ _____ _____ _____ _____amino acid sequence: amino acid sequence:

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