Biovet 2 - Replikasi - Kuliah - Slide Kulaih Replikasi Dna (

8/17/2019 Biovet 2 - Replikasi - Kuliah - Slide Kulaih Replikasi Dna (

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DNA andDNA and

ReplicationReplicationcopyright cmassengale


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HistoryHistory

of DNAof DNA

copyright cmassengale


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History of DNA

• Early scientists thoughtprotein was the cell’s

hereditary material becauseit was more complex thanDNA

• Proteins were composed of 2different amino acids in longpolypeptide chains



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!ransformation!ransformation

• "red #riffith wor$ed with%irulent & and non%irulent R strain Pneumoccocus bacteria

• He found that R strain couldbecome %irulent when it too$ inDNA from heat'$illed & strain

• &tudy suggested that DNA wasprobably the genetic material



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#riffith Experiment



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History of DNA

• (hromosomes are madeof both DNA andprotein

• Experiments onbacteriophage %irusesby Hershey ) (hase

pro%ed that DNA wasthe cell’s geneticmaterial

Radioacti%e *2P was in+ected into bacteria, copyright cmassengale


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Disco%ery of DNADisco%ery of DNA

&tructure&tructure• Erwin (hargaff showed theamounts of the four bases on

DNA - A.!.(.#/• 0n a body or somatic cell1 A *3*4

! *3*4 # 56374 ( 56364



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(hargaff’s Rule(hargaff’s Rule

• AdenineAdenine must pair with!hymine!hymine

• #uanine#uanine must pair with

(ytosine(ytosine• !he bases form wea$hydrogen bonds

# (! A



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DNA &tructureDNA &tructure

• Rosalind "ran$lin too$diffraction x'ray

photographs of DNAcrystals

• 0n the 567’s. 8atson )

(ric$ built the first model of DNA using "ran$lin’s x'rays



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Rosalind "ran$linRosalind "ran$lin



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DNADNA

&tructure&tructure



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DNADNA• !wo strands coiled calleda double helix

• &ides made of a pentosesugar Deoxyribose bondedto phosphate -P9:/ groupsby phosphodiester bonds

• (enter made of nitrogenbases bonded together bywea$ hydrogen bonds



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DNA Double HelixDNA Double Helix

NitrogenousNitrogenous;ase -A.!.# or (/;ase -A.!.# or (/


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HelixHelix

• ?ost DNA has a?ost DNA has a right'handright'hand twist withtwist with 5 base pairs5 base pairs in ain acomplete turncomplete turn

• >eft twisted DNA is called>eft twisted DNA is called@'DNA@'DNA oror southpawsouthpaw DNADNA

•Hot spotsHot spots

occur where rightoccur where right

and left twisted DNA meetand left twisted DNA meet

producingproducing mutationsmutations



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DNADNA• &tands forDeoxyribonucleic acid

• ?ade up of subunits callednucleotidesnucleotides • NucleotideNucleotide made of1made of1

53 Phosphate groupPhosphate group23 7'carbon sugar7'carbon sugar*3 Nitrogenous baseNitrogenous base



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DNA NucleotideDNA Nucleotide

9P'9 9

PhosphatePhosphate #roup#roup

NNitrogenous baseNitrogenous base -A. #. (. or !/-A. #. (. or !/

(H2

9

(5(:

(* (2

7

&ugar&ugar-deoxyribose/-deoxyribose/

copyr ight cmassengale


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Pentose &ugarPentose &ugar

• (arbons are numbered cloc$wise 5’to 7’

(H2

9

(5

(:

(* (2

7

&ugar&ugar-deoxyribose/-deoxyribose/



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DNA1DNA1 &trands are Antiparallel&trands are Antiparallel

P

P

P

9

9

9

5

2*

:

7

7

*

*

7

P

P

P

9

9

9

5

2 *

:

7

7

*

7

*

# (

! A



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A Polynucleotide

• MANYnucleotides

(“links”)bondedtogetherDNA has a

overall

negativecharge b/c of

the PO4-3

(phosphate

group)

Ph h di B d


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• Phosphodiester Bond

–The covlenttht holdstogether thebckbone

–!ound bet"eenP # deo$yribosesugr

–%T&'N


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Antiparallel &trandsAntiparallel &trands

• 9ne strand ofDNA goes from7’ to *’ -sugars/

• !he otherstrand isopposite in

direction going*’ to 7’ -sugars/



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Nitrogenous ;asesNitrogenous ;ases

• Double ringDouble ring PR0NE&PR0NE&

Adenine -A/Adenine -A/

#uanine -#/#uanine -#/

• &ingle ring&ingle ring PBR0?0D0NE&PBR0?0D0NE&

!hymine -!/!hymine -!/(ytosine -(/(ytosine -(/ ! or (

A or #



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;ase'Pairings;ase'Pairings

• Purines only pair with Pyrimidines

• !hree hydrogen bonds

reCuired to bond #uanine) (ytosine

(#

* H'bonds



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! A

•!wo hydrogen bonds arereCuired to bond Adenine )!hymine



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uestion1uestion1

• 0f there is *4

AdenineAdenine. how much(ytosine(ytosine is present



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Answer:Answer:

• !here would be 24(ytosine(ytosine

• Adenine -*4/ !hymineAdenine -*4/ !hymine-*4/-*4/• #uanine -24/ (ytosine#uanine -24/ (ytosine

-24/-24/• !herefore.!herefore. F4 A'! andF4 A'! and:4 ('#:4 ('#



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DNADNA

ReplicationReplication



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Replication "actsReplication "acts

• DNA has to be copiedDNA has to be copiedbefore a cell di%idesbefore a cell di%ides

• DNA is copied during theDNA is copied during the && or synthesis phase ofor synthesis phase ofinterphaseinterphase

• New cells will needNew cells will need identicalidenticalDNA strandsDNA strands



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&ynthesis Phase -& phase/&ynthesis Phase -& phase/

• & phase during interphase of thecell cycle

• Nucleus of eu$aryotes

?itosis'prophase'metaphase'anaphase

'telophase

#5 #2

&phase

interphase

DNA replication ta$esDNA replication ta$esplace in the & phase3place in the & phase3



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DNA ReplicationDNA Replication•

;egins at;egins at

9rigins of Replication9rigins of Replication

• !wo strands open forming!wo strands open forming ReplicationReplication"or$s -B'shaped region/"or$s -B'shaped region/

• New strands grow at the for$sNew strands grow at the for$s

ReplicationReplication"or$"or$

Parental DNA ?oleculeParental DNA ?olecule

*’

7’

*’

7’copyright cmassengale

• Chain elongation occurs in the 5' to3' direction by addition of onenucleotide at a time to the 3' end


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• As replication for!

"oves# onl$ % stran&can serve aste"plate forcontinuous *NA

synthesis'the leding strnd

• Opposite lgging

strnd un&ergoesdiscontinuous *NAsynthesis+


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DNA ReplicationDNA Replication

• As the 2 DNA strands open atAs the 2 DNA strands open atthe origin.the origin. Replication ;ubblesReplication ;ubbles formform

• Pro$aryotes -bacteria/ ha%e asingle bubble

• Eu$aryotic chromosomes ha%e?ANB bubbles

;ubbles ;ubbles



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• DNA replication

begins at the origino, repliction an& isbidirectionl ratherthan unidirectionl+

• A replicon is thelength of DNA that isreplicate& folloingone initiation event

at a single origin


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• EnGymeEnGyme HelicaseHelicase unwindsunwindsand separates the 2 DNAand separates the 2 DNAstrands by brea$ing thestrands by brea$ing the

wea$ hydrogen bondswea$ hydrogen bonds• &ingle'&trand ;inding&ingle'&trand ;indingProteinsProteins attach and $eep

the 2 DNA strandsseparated and untwisted



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• EnGymeEnGyme !opoisomerase!opoisomerase attachesto the 2 for$s of the bubble torelie%e stressrelie%e stress on the DNADNA

moleculemolecule as it separatesEnGyme

DNA

EnGyme



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• ;efore;efore new DNA strands canform. there must be RNARNAprimersprimers present to start the

addition of new nucleotides• PrimasePrimase is the enGyme that

synthesiGes the RNA Primer

• DNA polymerase can then addthe new nucleotides



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• DNA polymeraseDNA polymerase can only addcan only addnucleotides to thenucleotides to the *’ end*’ end of theof theDNADNA

• !his causes the!his causes the NE8NE8 strand to bestrand to bebuilt in abuilt in a 7’ to *’ direction7’ to *’ direction

RNARNAPrimerPrimerDNA PolymeraseDNA PolymeraseNucleotideNucleotide

7’

7’ *’



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&ynthesis of the New DNA&ynthesis of the New DNA&trands&trands

• !he!he >eading &trand>eading &trand issynthesiGed as a single strandsingle strandfrom the point of origin towardthe opening replication for$

RNARNAPrimerPrimerDNA PolymeraseDNA PolymeraseNucleotidesNucleotides

*’7’

7’



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&ynthesis of the New DNA&ynthesis of the New DNA&trands&trands

• !he!he >agging &trand>agging &trand isis synthesiGeddiscontinuouslydiscontinuously against o%erall direction ofreplication

• !his strand is made in ?ANB short segments 0t is replicated from the replication for$toward the origin

RNA PrimerRNA Primer

>eading &trand>eading &trand

DNA PolymeraseDNA Polymerase

7

’7’

*’

*’

>agging &trand>agging &trand

7’

7’

*’

*’ copyright cmassengale


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• DNA s$nthesis at a single replication

for!


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• *oth DNA stran&s are s$nthesi+e&

concurrentl$ b$ looping the laggingstran& to invert the ph$sical but notbiological &irection of s$nthesis


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>agging &trand &egments>agging &trand &egments

• 9$aGa$i "ragments9$aGa$i "ragments '' series ofshort segments on the lagginglaggingstrandstrand

• ?ust be +oined together by an?ust be +oined together by anenGymeenGyme

>agging &trand

RNARNA

PrimerPrimer

DNADNAPolymerasePolymerase

*’

*’

7’

7’

9$aGa$i "ragment9$aGa$i "ragment



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oining of 9$aGa$i "ragmentsoining of 9$aGa$i "ragments

• !he enGyme!he enGyme >igase>igase +oins the +oins the9$aGa$i fragments together to9$aGa$i fragments together to

ma$e one strandma$e one strand

>agging &trand

9$aGa$i "ragment 29$aGa$i "ragment 2

DNA ligaseDNA ligase

9$aGa$i "ragment 59$aGa$i "ragment 5

7’

7’

*’

*’



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Replication of &trandsReplication of &trands

Replication"or$

Point of 9rigin



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Proofreading New DNAProofreading New DNA

• DNA polymerase initially ma$esDNA polymerase initially ma$esaboutabout 5 in 5.5 in 5. base pairingbase pairing

errorserrors• EnGymesEnGymes proofread and correctproofread and correctthese mista$esthese mista$es

• !he new error rate for DNA that!he new error rate for DNA thathas been proofread ishas been proofread is 5 in 5 billion5 in 5 billion base pairing errorsbase pairing errors


d l f& i i ? d l f


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&emiconser%ati%e ?odel of&emiconser%ati%e ?odel ofReplicationReplication

• 0dea presented by0dea presented by 8atson ) (ric$8atson ) (ric$

• !he!he two strands of the parentalmolecule separate. and each acts as a

template for a new complementarystrand

• New DNA consists of 5

PAREN!A> -original/ and 5 NE8strand of DNAParental DNA

DNA !emplate

New DNA



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• 3 possible "o&esof DNA replicationare possible

– conservative

– se"iconservative

– &ispersive


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DNA Damage ) RepairDNA Damage ) Repair

• (hemicals ) ultra%iolet radiation damage the DNA in our body cells

• (ells must continuously repairDA?A#ED DNA

• Excision repair occurs when any ofo%er 7 repair enGymes remo%edamaged parts of DNA

• DNA polymerase and DNA ligase replace and bond the new nucleotidestogether



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uestion1uestion1

• 8hat would be thecomplementary DNA

strand for the followingDNA seCuence

DNA 7’'(#!A!#'*’DNA 7’'(#!A!#'*’



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Answer1Answer1

DNA 7’'(#!A!#'*’DNA 7’'(#!A!#'*’

DNA *’'#(A!A('7’DNA *’'#(A!A('7’



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51copyright cmassengale

Documents

Biovet 2 - Replikasi - Kuliah - Slide Kulaih Replikasi Dna (