New Gene Expression-doc viliran 6/11/09

8/14/2019 New Gene Expression-doc viliran 6/11/09

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GENEEXPRESSION

Dolores V. Viliran, MDDepartment of Biochemistry & Nutrition

FEU-NRMF,Institute of Medicine


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INTRODUCTION

5

5

3

3

Hydrogen bonds

3.4 nmG ~ CA ~ T


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INTRODUCTION

DNA

DNA

replication

RNA

transcriptionreverse

proteintranslation

Central Dogma of Molecular Genetics


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SCHEMA OF

GENE EXPRESSION


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Replication

(DNA Synthesis)


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Four Phases Of The Eukaryotic Cell CycleFour Phases Of The Eukaryotic Cell Cycle

M (mitotic) phase cell division occurM (mitotic) phase cell division occur

GG11 (gap) phase longest part of cell cycle(gap) phase longest part of cell cycle

1. Responsible for variation in cell cycle1. Responsible for variation in cell cycle

(8 hrs to >100 days)(8 hrs to >100 days)

2. Cells irreversible decision to proliferate is2. Cells irreversible decision to proliferate is

made heremade here - aided by cell division cycle proteins (CDC) which- aided by cell division cycle proteins (CDC) which

helpshelpscell to get beyond restriction pointcell to get beyond restriction point

- CDCs are protein kinases- CDCs are protein kinases


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B. Gap Phase cont.B. Gap Phase cont.

3. Cells may enter a quiescent phase (G3. Cells may enter a quiescent phase (Goo) )

cells do not divide e.g. neurons & muscle cellscells do not divide e.g. neurons & muscle cells

Factors that bring about quiescenceFactors that bring about quiescence

a) short supply of nutrientsa) short supply of nutrients

b) contact inhibition cell is in contact withb) contact inhibition cell is in contact with

other cellsother cells


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C. S (synthetic) phase only period when DNA isC. S (synthetic) phase only period when DNA is

synthesizedsynthesized

Factors that induce DNA synthesisFactors that induce DNA synthesis

2.2. Carcinogens and tumor virusesCarcinogens and tumor viruses

3.3. Surgical removal of a tumorSurgical removal of a tumor4.4. Mitogens proteins that bind to cell surfaceMitogens proteins that bind to cell surface

receptors and induce cell divisionreceptors and induce cell division


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Types of ReplicationTypes of Replication

1.1. Conservative replication one daughter DNAConservative replication one daughter DNA

conserves the parental DNA while the otherconserves the parental DNA while the other

daughter DNA gets the newly synthesizeddaughter DNA gets the newly synthesized

DNADNA

2. Semiconservative replication each daughter2. Semiconservative replication each daughter

DNA conserves one strand of parental DNADNA conserves one strand of parental DNA

and one strand of newly synthesized DNAand one strand of newly synthesized DNA

* type of replication in living organisms* type of replication in living organisms


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Replication

fork


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REPLICATION

formation of a new DNA strand using anotherDNA as template

occurs at the S phase [cell cycle]

location: nucleus, mitochondrion & chloroplast in

eukaryotes

semi-conservative [Messelson & Stahl]

rate: 500 nts are added per second

few hrs to duplicate the human genome

error rate: 1 mispaired base in 109 nts

results to a 4n chromosome number


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proteins involved:

1. Topoisomerases - removes the supercoils

2. DnaA - ~ 30 units form a barrel DNA wounds

3. DnaB - a Helicase; unwinds the DNA & breaks the

hydrogen bonds between the bases4. DnaC- binds transiently to the DNA

5. SSB - prevents renaturation of the unwound DNA

RNA Primer- ~10 nts synthesized by Primase

REPLICATION: Initiation

occurs at the oriC [E coli], ARS [fungi]numerous origins in one chromosome

oriC: three 13-bp sequences - first to melt

five 9-bp sequences - binding sites for DnaA


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REPLICATION: Elongation

3

3

5

5

helicase

SSB

Direction of replication fork

primase

DNA Polymerase III

DNA Polymerase I

LEADING STRAND

LAGGING STRAND

Ligase

Okazaki fragment


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REPLICATION: Elongation

DNA Polymerase IIIpolymerase function: 5 3 [ ]proofreading function: 3 5 exonuclease [ ]

Primase - synthesizes the RNA primer

DNA Polymerase I - replaces the primer with DNA

DNA Ligase - connects adjacent okazaki fragments

Eukaryotic DNA Polymerase

DNA Pol - primingDNA Pol - DNA repairDNA Pol - mitochondrial DNA replicationDNA Pol - main replicative enzymeDNA Pol - unknown function


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REPLICATION: termination

termination sites [Ter A - E] which are binding

sites forTUS [terminator utilization substances]

Shortening of the Telomere


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Things to remember ...

replication starts at the oriC and ends at the Ter

DNA Polymerase III is the main replicative enzyme

direction of replication: 5 3

templates used: both strandsreqts for initiation: template, RNA primer, DNA Pol III

leading strand - replicated continuously

lagging strand - replicated discontinuously[okazaki]linear chromosomes tend to shorten after replication

Tx: telomerase - not found in all cells

Fidelity: proofreading, excision repair, mutator proteins


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LegendLegend


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Dna replication in actionDna replication in action


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Gene TranscriptionGene Transcription(RNA Synthesis)(RNA Synthesis)


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TranscriptionTranscription

Biosynthesis of RNABiosynthesis of RNA

RNA copies of selected DNA sequencesRNA copies of selected DNA sequences(genes) are made(genes) are made


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GeneGene

Classical definitionClassical definition

A gene is a segment of DNA thatA gene is a segment of DNA that

determines a single character ordetermines a single character orphenotypephenotype

e.g., eye color, facial features,e.g., eye color, facial features,

height, etc.height, etc.


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GeneGene

Molecular definitionMolecular definition

A gene is a segment of DNA thatA gene is a segment of DNA that

codes for:codes for: One enzymeOne enzyme

One proteinOne protein

One polypeptideOne polypeptide One RNAOne RNA


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Types of Gene from Standpoint ofTypes of Gene from Standpoint of

FunctionFunctionA.A. Structural GenesStructural Genes

Codes for polypeptides and RNAsCodes for polypeptides and RNAs

B.B. Nonstructural GenesNonstructural Genes

Operator geneOperator gene one that serves as a one that serves as a

starting point for reading the genetic codestarting point for reading the genetic code

Regulator geneRegulator gene one that synthesizes one that synthesizesthe repressor (a substance whichthe repressor (a substance which

switches off the activity of the structuralswitches off the activity of the structural

gene).gene).


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Definition of TermsDefinition of Terms

CistronCistron

Smallest unit of DNA which must be intactSmallest unit of DNA which must be intact

so that it can serve as transmitter ofso that it can serve as transmitter ofgenetic informationgenetic information

MutonMuton

Smallest unit of DNA whose alteration canSmallest unit of DNA whose alteration cangive rise to a mutant form of organismgive rise to a mutant form of organism


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ReconRecon

Smallest unit of DNA capable ofSmallest unit of DNA capable ofrecombination, presumably a series of threerecombination, presumably a series of three

nucleotide bases (triplet).nucleotide bases (triplet).

RecombinationRecombination Formation of a new combination of genesFormation of a new combination of genes

IntronsIntrons

Intervening segments of DNA that do notIntervening segments of DNA that do notcode for the amino acid sequence of thecode for the amino acid sequence of the

polypeptide (function is probably regulatory)polypeptide (function is probably regulatory)


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ExonsExons

Coding segments of the geneCoding segments of the gene

ChromosomeChromosome

A structure in the nucleus containing theA structure in the nucleus containing the

chromatin material made up of:chromatin material made up of:

65% protein (histones)65% protein (histones)35% DNA35% DNA

5% RNA5% RNA

There are so many genes in a singleThere are so many genes in a singlechromosome, e.g. E. coli = 3,000 to 5,000chromosome, e.g. E. coli = 3,000 to 5,000

genesgenes

Chromatin fibers resemble a string of beadsChromatin fibers resemble a string of beads


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NucleosomeNucleosome

Repeating beadlike structures composed of:Repeating beadlike structures composed of:

Segment of DNA duplex (about 200Segment of DNA duplex (about 200

base pairs)base pairs)

Eight histone molecules (two each ofEight histone molecules (two each of

HH22A, HA, H22B, HB, H33 and Hand H44))


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HistonesHistones

Found only in eukaryotesFound only in eukaryotes Function is to package and order DNA intoFunction is to package and order DNA into

structural units called nucleosomesstructural units called nucleosomes

HH11 = lysine-rich= lysine-rich

HH22A and HA and H22BB = large amount of lysine= large amount of lysine

and arginineand arginine

HH33 and Hand H44 = arginine-rich= arginine-rich


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TRANSCRIPTION

formation of RNA using a DNA as template

involves a short fragment of the genetic material only

only one of the 2 strands is used as template

direction of transcription: 5 3

location: nucleus, mitochondria, chloroplasts

occurs in most phases of the cell cycle

regulation: via Methylation of the CpG islands of genes

housekeeping genes are never methylated

rate: ~ 1,500 nts are transcribed in 50 seconds


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TRANSCRIPTION

DNA-dependent RNA Polymerase [RNAP]main enzyme involved in transcription

components: 1) core enzyme-

- polymerase function2) sigma factor

- regulatory function

no proofreading capacity [less accurate than

DNA Polymerase III; prone to more errors]

Eukaryotic RNAPs:

RNAP I - transcribes rRNAsRNAP II - transcribes mRNAsRNAP III - transcribes tRNAs


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A typical transcriptional unit

promoter Informative sequence terminator

DNA

TATACAATGC

+1 +N-100 -10

Transcriptional start point

-80

TATA box - aka Pribnow box; recognition site of sigma factor

CAAT box - influences rate & frequency of transcription

GC box

octomers


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DNA

GGCCGGCCGGCC------AAAAAAAAAAAAA

GC-rich region = allows hairpin loop formation

poly-A tract = allows dissociation of RNAP


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DNA

Initiation codon Polyadenylation signal

Stopcodon

AAAAAAAAA

Primary transcript

Mature mRNA


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DNA before transcription

5

53

3

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

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


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During transcription, The DNA should unwind so that one of its strand can be used as

template to synthesize a complementary RNA.

5

53

3

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

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

G T A G C T G C

C A T C G A C G

5 3

C A U C

RNA


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TRANSCRIPTION: steps

RNAP factor

CLOSED promoter complex

OPEN promoter complex

Initiation

Elongation


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TRANSCRIPTION


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TRANSCRIPTION

Termination Signals1) Rho-independent = GC-rich + poly-A tract

2) Rho-dependent = GC-rich + Rho protein

Modification of mRNAs1) Capping = addition of5-methylguanosine cap;

occurs after the 5 end has been synthesized

2) Polyadenylation = addition of the 3-poly-A tail;

requires a clipping enzyme [5-AAUAAA-3]and the Poly-A polymerase

3) Splicing of exons = removal of the introns and

splicing of the exons; follows the AG-TG rule


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TRANSCRIPTION

Splice junctions:AG-TG rule

A AGGT

Exon 1 Exon 2

Intron

subsequent to capping & polyadenylation

prior to migration from the nucleus

reqts: small nuclear ribonucleoprotein

particles [snRNPs] and snRNAs

[U1,U2, U4, U5 and U6]


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COMPARISON

Replication Transcription

Location nucleus, mt, chpt nucleus, mt, chpt

Enzyme DNA Pol III RNAP

Direction 5 3 5 3

Template both strands one strand

antisense

Primer needed not required

Target seq. entire genome a gene

Accuracy

Units dNTPs: thymine NTPs: uracil


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TRANSLATION

synthesis of a polypeptide based on an mRNAtemplate

location: cytoplasm [ribosomes]

requirements:

1) mRNA - with codons

2) tRNAs - with anti-codon

3) amino acids

main enzyme: peptidyl transferase

translational rate: ~ 15 amino acids/second

in E coliat 37o C


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GENETIC CODEGENETIC CODE- maps DNA sequences to proteins in the living celL- maps DNA sequences to proteins in the living celL

- It is the sequence of bases (CODONS) in the- It is the sequence of bases (CODONS) in themRNA which determines the protein that will bemRNA which determines the protein that will besynthesizedsynthesized

CODON - 3 base words (4CODON - 3 base words (433

))- 64 possible trinucleotide sequences are present- 64 possible trinucleotide sequences are present

61 = code for amino acid61 = code for amino acid

3 = stop codons3 = stop codons

Starting codon = AUGStarting codon = AUG- marks the start of a protein sequence- marks the start of a protein sequence

End Codons = UAA, UAG, or UGAEnd Codons = UAA, UAG, or UGA


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Properties of Genetic codeProperties of Genetic code


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Properties of Genetic codeProperties of Genetic code

Degenerate amino acids are coded by several codon or somecodons may code for the same amino acid

e.g. UUA,UUG,CUU,CUC,CUA and CUG codes of leucine

Specific Each codon signals for a specific amino acid Non-overlapping and without punctuation/commaless

the mRNA coding sequence is read by a ribosome startingfrom the initiating codon (AUG) as a continuous sequence takenthree bases at a time until a stop codon is reached.

Reading frame set of continuous triplet codons in a mRNA

Universal Examinations of the translation process in the species

that have been investigated have revealed that the coding signals foramino acids are always the same.[though there are someexceptions, especially in the mitochondrial and chloroplast DNA],


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Codons Anticodon InteractionCodons Anticodon Interaction

The base pairing between the anticodon of the tRNAThe base pairing between the anticodon of the tRNAand the mRNA codon is responsible for the actualand the mRNA codon is responsible for the actual

translation of the genetic information of structuraltranslation of the genetic information of structuralgenes. Although codon-anticodon pairings aregenes. Although codon-anticodon pairings areantiparallel, both sequences are given in the 5 -> 3antiparallel, both sequences are given in the 5 -> 3direction.direction.

ex. AUG binds to anticodon CAUex. AUG binds to anticodon CAU

- the pairing of the codon (AUG) and anticodon- the pairing of the codon (AUG) and anticodon(CAU) ensures that the amio acid will be(CAU) ensures that the amio acid will beincorporated into a growing polypeptide chain.incorporated into a growing polypeptide chain.

Most cells possess about 50 tRNAs and some of the anticodonMost cells possess about 50 tRNAs and some of the anticodoncontains uncommon nucleotides such as inosinate (I) whichcontains uncommon nucleotides such as inosinate (I) whichtypically occur at the third anticodon.typically occur at the third anticodon.


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Codon-anticodonCodon-anticodon

5

3

5

3

A=====U

U=====A

G=====C

tRNA

mRNA


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WOBBLE HYPOTHESIS- The first two bases are important in identifying their

cognate amino acids

- The third base [called the wobble base] is not asimportant, pursuant to the Wobble theory of thegenetic code

- Wobble theory suggested that while the interactionbetween the codon in the mRNA and the anticodonin the tRNA needed to be exact in two of the threenucleotide positions, this did not have to be so in thethird position

- The theory proposed that non-standard base-pairingmight occur between the nucleotide base in the 5'position of the anticodon and the 3' position of thecodon.

5 anticodon base 3 codon base


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A

C

G

U

I

U

C or U

A or G

A or C or U

G

5 anticodon base 3 codon base


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TRANSLATION

Messenger RNA [mRNA]

Initiation codon Stop codon

AAAAAUG UGA PASSD

Shine Dalgarno Sequence - the ribosome binding site

AUG - initiation codon; contained within the Kozak

sequence in eukaryotesStop codons - UGA, UAG, UAA

PAS - Polyadenylation signal

NOTE: mRNA is derived from heterogeneous nuclear RNA

[hnRNA] in eukaryotes

codons


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TRANSLATION

Transfer RNA [tRNA]

cloverleaf appearance

adaptor molecule

~ 61 types of tRNAs

Pre-Initiation Phase: Charging of tRNA


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TRANSLATION

Ribosomes

prokaryote eukaryote

small subunit 30S 40S

large subunit 50S 60S

complete unit 70S 80S

the small and large subunits combine afterthe initiation of

translation

small subunit = + mRNA binding site [16S RNA]

large subunit = + tRNA binding sites [P & A sites]

16S rRNA of the small subunit is highly

conserved


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Initiation Step

1) Dissociation of 70S [IF1]

2) Binding of IF3 to 30S

3) Binding of IF1 & IF2-GTP

4) Formation of the Pre-Initiation Complex

5) Binding of 50S to 30S &

loss of IF1 & IF3

6) Loss of IF2 and hydrolysis

of GTP GDP + Pi

El ti


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Elongation

1) Second aa-tRNA enters

the A site

2) Peptide bond formation

via Peptidyl transferase

[23S rRNA of the large

subunit]

3) mRNA moves to the left

Termination


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Termination

occurs when a stop codon occupies the A site

UGA - opal codon

UAG - amber codonUAA - ochre codon

no tRNA has the anticodon for the stop codons

a release factorrecognizes these stop codons,

attaches to the A site and breaks up the complex

AAAAUGA

Release factor


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Protein folding - proper folding of nascent polypeptidemade possible by molecular chaperones

HSP 70 - prevents premature folding

GroeL/GroeS - cage-like structures that prevents

aggregation of unfolded proteins

Intein Splicing - removal of inteins and the ligation of exteinsInteins - intervening, non-informative aa sequencesExteins - informative aa sequences

Signal peptide: ~ 20 aa, for proteins destined forendomembrane system or for secretion; recognized by

the Signal Recognition Peptide [SRP; brings the ribosome to ER]

Proteolytic cleavage - polyproteins are cleaved to yieldseveral active proteins [ex. Proopiomelanocortin]

Post-translational Modification


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ANTIBIOTICS BY SITE OFANTIBIOTICS BY SITE OF

ACTIONACTION A. Protein synthesis inhibitorsA. Protein synthesis inhibitors

30S ribosomal subunit30S ribosomal subunit

Aminoglycosides(streptomycin), tetracyclineAminoglycosides(streptomycin), tetracycline 50S ribosomal subunit50S ribosomal subunit

Chloramphenicol binds tp 50S and inhibitsChloramphenicol binds tp 50S and inhibits

peptidyl transferasepeptidyl transferase

Erythromycin and Clindamycin binds to 50 SErythromycin and Clindamycin binds to 50 S

and prevent translocationand prevent translocation



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ACTIONACTION

A. Protein synthesis inhibitorsA. Protein synthesis inhibitors

60S ribosomal subunit60S ribosomal subunit

Cycloheximide binds to 60S,inhibits peptidylCycloheximide binds to 60S,inhibits peptidyl

transferasetransferase A and P sitesA and P sites

Puromycin an amino acid analog, binds APuromycin an amino acid analog, binds A

site,prevents eukaryotic and prokaryoticsite,prevents eukaryotic and prokaryotic

translationtranslation

eEF-2eEF-2

Diphtheria toxin inhibits eukaryotic elongationDiphtheria toxin inhibits eukaryotic elongation

factor 2factor 2


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ACTIONACTION RNA synthesis inhibitorsRNA synthesis inhibitors

Prokaryotic RNA polymeraseProkaryotic RNA polymerase

Actinomycin binds to DNAActinomycin binds to DNA Rifampin binds toRifampin binds to -subunit of RNA-subunit of RNA

polymerasepolymerase

Eukaryotic RNA polymerase IIEukaryotic RNA polymerase II

Amanita phylloides- angel of DeathAmanita phylloides- angel of Death

mushroom inhibits RNA pol IImushroom inhibits RNA pol II


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ACTIONACTION DNA synthesis inhibitorsDNA synthesis inhibitors

DNA gyrase inhibitorsDNA gyrase inhibitors

QuinolonesQuinolones DNA topoisomerase inhibitorsDNA topoisomerase inhibitors

Nalidixic acidNalidixic acid

NovobiocinNovobiocin


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Other Medications: inhibitsOther Medications: inhibits

deoxythymidylate synthesisdeoxythymidylate synthesis 1. Folic acid analog1. Folic acid analog

inhibitor of dihydrofolate reductaseinhibitor of dihydrofolate reductase

MethotrexateMethotrexate

AminopterinAminopterin

2. Inhibits Thymidylate Synthesis2. Inhibits Thymidylate Synthesis

5-Fluorouracil5-Fluorouracil


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LIST OF INHIBITORS

Coumarine inhibits DNA gyrase by competing with ATPQuinolones inhibits DNA gyrase by binding its amino terminus

Rifampicin inihibits RNA polymerase by binding to its chain

Chloramphenicol binds to 50S and prevents peptide bond formation

Erythromycin inhibits translocation of 50S subunit

Fusidic acid inhibits translocation by preventing dissociation of

EF-G-GDP from ribosome

Puromycin an aa-tRNA analog causing premature chain termn

Tetracycline binds to 30S subunit and prevents aa-tRNA binding

to the A site

Cyclohexamide inhibits peptidyl transferase on eukaryotic 60SDiphtheria toxin inhibits eukaryotic EF-2 by ADP ribosylation

Streptomycin binds to 30S subunit & causes mRNA misreading

Kanamycin binds to 70S unit and causes mRNA misreading


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A U G U C U C C G U A A

mRNA

Ribosome binding protein

Small ribosomal

subunit

Large ribosomal

subunit


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Small ribosomal

Subunit binds to

mRNA


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P site on ribosomes

A site on ribosomes

Large ribosomal

subunits binds to

small subunit

forming complete

ribosomes


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U A C codonsAnti-codon

tRNA

Amino Acid (Met)


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U A C

First, tRNA binds at

the P-site

Anti-codon matches initiating codon on mRNA


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A U G U C U C C G U A AU A C

A G A

Next tRNA with

different anti-codonand amino acid


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A U G U C U C C G U A AU A C

A G A

Second tRNA binds in the A

site of the ribosome andmatches the next codon


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A U G U C U C C G U A AU A CA G A

Amino acid moved from

first tRNA and joined to

second tRNA forming a

di-peptide


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A U G U C U C C G U A AU A CA G A

Empty tRNA is released

Ribosomes moves and the tRNA with di-

peptide moves to P-site


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A U G U C U C C G U A AA G A

G G C

Third tRNA with amino

acid arrives


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A U G U C U C C G U A AA G A

G G C

Third tRNA with amino

acid arrives

Codon matches anti-codon

tRNA moves onto A-site


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A U G U C U C C G U A AA G A G G C

Di peptide moved and Tri-peptide formed


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A U G U C U C C G U A AA G A G G C

empty tRNA moves off ribosome

Ribosomes moves

tRNA moves to P-site


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A G A

A U G U C U C C G U A AG G C

empty tRNA moves off ribosome

Ribosomes moves

tRNA moves to P-site

Termination signal

no anti-codon on any tRNA


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Complete polypeptide is released


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Complete polypeptide is released

Ribosome units separate

Wh i h ibl l fWh t i th ibl l f


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What is the possible role ofWhat is the possible role of

modified histones?modified histones?A. methylation of histones is correlated withA. methylation of histones is correlated with

activation and repression of geneactivation and repression of gene

transcriptiontranscription

B. Methylation of histones leads to transcriptionB. Methylation of histones leads to transcription

activation onlyactivation only

C. Phosphorylation of histones H3 and H4 isC. Phosphorylation of histones H3 and H4 is

associated with the condensation ofassociated with the condensation ofchromosomes during the replication cyclechromosomes during the replication cycle

D. Acetylation of histone H1 is associated withD. Acetylation of histone H1 is associated with

chromosomal assembly during DNAchromosomal assembly during DNA

Wh i h ibl l fWh t i th ibl l f


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What is the possible role ofWhat is the possible role of

modified histones?modified histones?A. methylation of histones is correlated withA. methylation of histones is correlated with

activation and repression of geneactivation and repression of gene

transcriptiontranscription

B. Methylation of histones leads to transcriptionB. Methylation of histones leads to transcription

activation onlyactivation only

C. Phosphorylation of histones H3 and H4 isC. Phosphorylation of histones H3 and H4 is

associated with the condensation ofassociated with the condensation ofchromosomes during the replication cyclechromosomes during the replication cycle

D. Acetylation of histone H1 is associated withD. Acetylation of histone H1 is associated with

chromosomal assembly during DNAchromosomal assembly during DNA

Whi h i id dWhi h i id d


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Which is considered asWhich is considered as

transcriptionally active chromatintranscriptionally active chromatinA. euchromatinA. euchromatin

B. heterochromatinB. heterochromatin

C. constitutive chromatinC. constitutive chromatin

D. telomeresD. telomeres

Whi h i id dWhi h i id d


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Which is considered asWhich is considered as

transcriptionally active chromatintranscriptionally active chromatinA. euchromatinA. euchromatin

B. heterochromatinB. heterochromatin

C. constitutive chromatinC. constitutive chromatin

D. telomeresD. telomeres

The genetic code is characterizedThe genetic code is characterized


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gg

as:as:

A. non-degenerateA. non-degenerate

B. non-overlappingB. non-overlapping

C. species-specificC. species-specific

D. non-specificD. non-specific

The genetic code is characterizedThe genetic code is characterized


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gg

as:as:

A. non-degenerateA. non-degenerate

B. non-overlappingB. non-overlapping

C. species-specificC. species-specific

D. non-specificD. non-specific

The precise initiation codon isThe precise initiation codon is


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determined by:determined by:

A. shine-Dalgarno sequenceA. shine-Dalgarno sequence

B. Kozak sequenceB. Kozak sequence

C. Consensus sequenceC. Consensus sequence

D. Repetitive sequenceD. Repetitive sequence



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determined by:determined by:

A. shine-Dalgarno sequenceA. shine-Dalgarno sequence

B. Kozak sequenceB. Kozak sequence

C. Consensus sequenceC. Consensus sequence

D. Repetitive sequenceD. Repetitive sequence

The first tRNA that enters the P siteThe first tRNA that enters the P site


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during translation process.during translation process.

A. Lys tRNAA. Lys tRNA

B. Met tRNAB. Met tRNA

C. Ala tRNAC. Ala tRNA

D. Glut RNAD. Glut RNA

The first tRNA that enters the P siteThe first tRNA that enters the P site


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during translation process.during translation process.

A. Lys tRNAA. Lys tRNA

B. Met tRNAB. Met tRNA

C. Ala tRNAC. Ala tRNA

D. Glut RNAD. Glut RNA

Factors that can cause DNAFactors that can cause DNA


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denaturation:denaturation:

A. Alkaline pHA. Alkaline pH

B. High temperatureB. High temperature

C. Acidic pHC. Acidic pH

D. A and BD. A and B

E. B and CE. B and C

Factors that can cause DNAFactors that can cause DNA


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denaturation:denaturation:

A. Alkaline pHA. Alkaline pH

B. High temperatureB. High temperature

C. Acidic pHC. Acidic pH

D. A and BD. A and B

E. B and CE. B and C

Which enzyme is needed forWhich enzyme is needed forsynthesis of the eukaryotic DNAsynthesis of the eukaryotic DNA


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synthesis of the eukaryotic DNAsynthesis of the eukaryotic DNA

lagging strandlagging strandA. DNA polymerase alphaA. DNA polymerase alpha

B. DNA polymerase sigmaB. DNA polymerase sigma

C. DNA polymerase IIIC. DNA polymerase III

D. DNA polymeraseD. DNA polymerase

Which enzyme is needed forWhich enzyme is needed forsynthesis of the eukaryotic DNAsynthesis of the eukaryotic DNA


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synthesis of the eukaryotic DNAsynthesis of the eukaryotic DNA

lagging strandlagging strandA. DNA polymerase alphaA. DNA polymerase alpha

B. DNA polymerase sigmaB. DNA polymerase sigma

C. DNA polymerase IIIC. DNA polymerase III

D. DNA polymeraseD. DNA polymerase

Which enzyme can remove theWhich enzyme can remove the


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yy

supercoiling produced duringsupercoiling produced during

replicationreplicationA. HelicaseA. Helicase

B. TopoisomeraseB. Topoisomerase

C. PrimaseC. Primase

D. Single-strand binding proteinD. Single-strand binding protein

Which enzyme can remove theWhich enzyme can remove the


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yy

supercoiling produced duringsupercoiling produced during

replicationreplicationA. HelicaseA. Helicase

B. TopoisomeraseB. Topoisomerase

C. PrimaseC. Primase

D. Single-strand binding proteinD. Single-strand binding protein


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Matching Type:Matching Type:

__16. mRNA serves as template__16. mRNA serves as template A. TranscriptionA. Transcription__17. TATA Box plays a crucial role__17. TATA Box plays a crucial role B. TranslationB. Translation

__18. May or may not require a rho facto C. Replication __18. May or may not require a rho facto C. Replication

__19. This is initiated with activation step D. A/B __19. This is initiated with activation step D. A/B

__20. An essential process in cell divisio E. A/B/C __20. An essential process in cell divisio E. A/B/C


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Matching Type:Matching Type:

_B_16. mRNA serves as template_B_16. mRNA serves as template A.A.TranscriptionTranscription

_A_17. TATA Box plays a crucial role_A_17. TATA Box plays a crucial role B.B.

TranslationTranslation

_A_18. May or may not require a rho facto C. _A_18. May or may not require a rho facto C.

ReplicationReplication _B_19. This is initiated with activation step D. _B_19. This is initiated with activation step D.

A/BA/B

_C_20. An essential process prior to division of cell E. _C_20. An essential process prior to division of cell E.

A/B/CA/B/C


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