Elite Batch 2012

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Elite Dental Team

: - DNA Replication

: - 1st exam - summer semester 2011

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- Q1 : question give us purine and pyrimydin and said what is that ?

-means that you need to know their shapes u need to know that (( T=G ))

=> is a mutation

- Q2 : if a prokaryotic cell copy DNA by a rate of (( 100 nucleotide => 1 min )) ,

how much time will spend to achieve 600 nucleotide ..

- not 6 min , cause its bidirectional ! - I think it will be 3 min or less than that

.. u need to think how many DNA pol you have ? if they are 4 it would be 1:30

minutes only .

- Q3 : function of DNA-pol ???

- repairing

- Q4 : question about Topoisomerases as drug targets ??? -DNA topoisomerases catalyze changes in the topology of DNA. A major goal of cancer therapy research is identification of critical biochemical targets that mediate the ability of effective cancer chemotherapy to kill tumor cells while allowing the maintenance of normal cell function. A candidate for such a target is DNA topoisomerase II, a ubiquitous enzyme that alters three-dimensional conformation of supercoiled DNA. - Q5 : Qeustion about Exonuclease functions ??/ -35 exonuclease activity === excise mismatched nuleotides

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Elite Dental Team

- Q6 : Question from the slide below => remember them all !

Q 7: you need to differentiate between base and nucleotide excision ! ???

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Elite Dental Team

Q8 : Questions for the slide below , type of qus : the example and what the type of

it ?

eg : - mitomycin c ? its an intersrand cross-link - belomycin ? strand break ..

- Q12 : Very important ! qus in the first and also in the final

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Elite Dental Team

: DNA Replication

: 1st exam 2012

Q1- DNA replication originates at the indicated origin of replication. Which

segment(s) serve as template(s) for lagging strand synthesis ?!

a) B & D

b) A & C

c) D

d)B

Q2- The nucleotides below are joined by ?!

a) 2'_5' Phosphodiester Bond

b)3'_5' Phosphodiester Bond

c)Glycoside Bond

d)5'_5' Phosphodiester Bond

e)2'_2' Phosphodiester Bond

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Elite Dental Team

Q3- When DNA replication originates at the indicated origin of replication ,

segment A will act as a template for

A) Continuous strand synthesis at a replication fork moving leftward as

drawn

B) Discontinuous strand synthesis at replication fork moving leftward as drawn

C) Continuous strand synthesis at a replication fork moving rightward as drawn

D) Discontinuous strand synthesis at replication fork

Q4- A strain of E-coli has a mutation eliminating the 5'exonuclease activity of

DNA Pol III . This strain is expected to show :

a) An increased mutation frequency .

b) A decreased mutation frequency .

c) An inability to join Okazaki fragment

d) Continuous strand synthesis only

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Q5- DNA polymerase I initiates at the end of Okazaki fragment and

further elongates the DNA chain with it's activity while

simultaneously removing the RNA primer with it's activity .

a) 5' to 3' Exonuclease , 5' to 3' Exonuclease

b) 3' to 5' Exonuclease , 3' to 5' Exonuclease

c) 5' to 3' Polymerase , 3' to 5' Exonuclease

d) 3' to 5' Exonuclease , 5' to 3' Polymerase

e) 5' to 3 Polymerase , 5' to 3' Exonuclease

Q6- How many each of the following is required to synthesis one DNA lagging

strand in prokaryotes ?

a) 1 RNA polymerase ( primase ) , 2 DNA polymerase and 1 DNA ligase

b) 2 RNA polymerase ( primase ) , 2 DNA polymerase and 1 DNA ligase

c) 1 RNA polymerase ( primase ) , 1 DNA polymerase and 1 DNA ligase

d) 1RNA polymerase ( primase ) , 2 DNA polymerase and 0 DNA ligase

e) 1 RNA polymerase ( primase ) , 3 DNA polymerase and 1 DNA ligase

Q7- Choose the incorrect association between the enzyme and it's function :

a) DNA polymerase alpha . Primer synthesis

b) DNA polymerase beta . Primer removal

c) Delta DNA polymerase lagging and leading strands synthesis

d) Epsilon DNA polymerase extending the Okazaki fragment

e) DNA ligase .. sealing nicks

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Q8- What is the type of mutation :

Normal sequence CATTCACCTGTACCA

GTAAGTGGACATGGT

Mutant sequence CATGTCACCTGTACCA

GTACAGTGGACATGGT

a) Transversion

b) Transition

c) Insertion

d) Deletion

e) Spontaneous

Q9- Tautomer formation of C during replication will result in mispairing and

insertion of in one of the daughter strands ?

a) A

b) G

c) T

d) U

e) X

Q10- Which of the following enzymes is not required when the DNA lesion is

thymedine dimer ??

a) Excinuclease

b) Repair nuclease

c) DNA polymerase b

d) DNA ligase

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Elite Dental Team

Q11- " Hot spots " mutations regions are rich in :

a) AT

b) AA

c) GG

d) CG

e) CC

Q12- Some eukaryotic cells have a specialized mismatch repair system that

recognizes G-T mismatches and changes them to G-C ( never to A-T) regardless of

which nucleotide is in the parental strand . This system safeguards against :

a) Methylated Cytosines that determinate to Thymine

b) Methylated guanines that determinate to Adenine

c) The inability of the generalized repair system to recognize G-T mismatchs

d) Mismatches that remain after it is too late to discriminate between the

parental and daughter strand

e) Formation of thymine dimmers

Q13- Which of the following is a target to fluoroquinolone antibiotics ?

a) DNA transcription

b) Protein synthesis

c) RNA polymerase II

d) DNA polymerase III

e) DNA gyrases

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Q14- Shown below a table of enzymes or proteins and the associated

function of each . Choose the incorrect association :

a) Rep protein .. helicase " unwind the DNA fork "

b) SSB ... binds to single stranded DNA

c) DNA pol III .. primary replicating polymerase

d) DNA pol I removes primer and fills gap

e) DNA ligase . Filling the gap between Okazaki fragments

Q15 - A heavy smoker developed lung tumor because of guanine oxdative

modification that causes G T transversions . which of the following genes is

most probably defected ?

a) MTH1

b) PCNA

c) HNPCC

d) DNA helicase gene

e) DNA methylase gene

Q16- The DNA pol I activity that can excise mismatched nucleotides :

a) 5' 3' exonuclease

b) 3' 5' exonuclease

c) 5' 3' polymerizing activity

d) 3' 5' polymerizing activity

Q17- U.V cause what kind of mutation ?

answer : dimmers

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Q18- Familial hypercholesterolemia caused by ?

answer : mutation of LDL receptor

Q19- mutation of DNA pol I ?

answer : replication with no fidelity

Q20- Telomerase activity in eukaryotic DNA act on :

a) Leading strand

b) Lagging strand

c) Both leading and lagging strands

: DNA replication

: 1st exam test bank

Q1- which of the following is responsible for correction of pyrimidine dimers in

human :-

a) Base excision repair

b) Nucleotide excision repair

c) Enzymatic demethylation

d) Mismatch repair

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Q2- If DNA synthesis initiates at the indicated origin of replication, Which

segments single stranded-DNA are templates for synthesis of Okazaki fragments:

a)B &C

b)A &B

c)A&C

d)B & D

Q3- Which of the following subunits of DNA polymerase III has 3`exonuclease

activity ?

a) Gamma subunit

b) Alpha subunit

c)Epsilon subunit

d) Theta function

e) Beta subunit

Which enzyme has an associted RNA that act as a template for DNA synthesis -Q4

??

a) Telomerase

b) RNase

c) Peptidyle transferase

d) Nucleotidyle transferase

ee) Reverse transcriptas

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following exceptinitiation of replication in prokaryotes includes all of the -Q5

a)DNaA

b)DNaB

c)DNaC

d)Helicase

e)Sliding clamp

which of the following eukaryotic DNA polymerases is associated with PCNA-Q6

a)Alpha

b)Gamma

c)Delta

d)Epsilon

Q6-Methylcytosines are common sites for mutations because they:-

a)can mispair with adenine

b)can deaminate to Uracil

c)can deaminate to Xanthine

d)When deaminated prevent discrimination between daughter & parental

strand

e)are not recognized by the proofreading activity of DNA polymerase

Q7-The primary cause of Fragile X syndrome is :

a)Chromosomal deletion

b)An expansion trinucleotide repeates

c)Amutation in an oncogene

e)Activation of telomerase

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Q8-Subsituation of G instead of A is called :- =))

a)transition

b)transversion

c)triplet expansion

d)pyrimidine dimer

e)purine dimer

coli is example of : -directed DNA repair pathway of E -Methyl -Q9

a) Mismatch repair system

b) Nucleotide excision repair system

c) Base excision repair system

d) Recombination repair system

e) photolyase reverse system

-The main replicative DNA polymerase on E.Coli is :-Q10

a)DNA polymerase I

b) DNA polymerase II

c) DNA polymerase III

11 Removal of RNA primers is a main function of which of the following -Q

eukaryotic enzymes ?

a) RNAaseH

b) Replication protein A

loading factor -Clampc)

d) DNA gyrase

e) DNA ligase

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Elite Dental Team

-Adjecent nucleotides are joined by :-Q12

a)purine

b)3'_5' phosphodiester bond

c) Glycosidic bond

d) Deoxuribose

-: The two exonuclease activities of DNA polymerase I-Q13

a) Occure at two different active site

b) Are coupled during the formation of 'gapped DNA '

3' direction -c) Degrade DNA in 5'

in 3'to5' direction d) Degrade DNA

-What is the enzyme that has 3' to 5' exonuclease activity :-Q14

a)DNA gyrase

b)RuvB

c)DNA polymerase III

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-Which of the following Not required for DNA replication : -Q15

a)Mg

b)DNA polymerase

c)dNTP

d)a+c

olysomes Pe)

A mutation is defined as : -Q16

a)A change in an organisms' DNA

b)The growth of an abnormal cell structure

change of a cell from one type to another c)The

d)a way of changing mRNA into protein

Which of the following illustrates a single point mutation on a segment of -Q17

DNA which leads ;TACACGGTG

TACACGCTGa.TACACGTGTG b.

d. TTCACGGAGGTGGCACAT c.

Which of the following illustrate a frame shift mutation on a segment of -Q18

DNA that TACACGGTG :

b.TACACGGTG TACACGTGTG a.

c.GTGGCACAT d. TTCACGGAG

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About deamination of cytosine , what is wrong : -Q19

a- Leads to the formation of uracil

b- It is a transition mutation

c- It is a point mutation

d- It is corrected by nucleotide excision repair

e- None of the above

Q20- About spontaneous damage in DNA , what is wrong :

a- It involves the depurination of the purine hypoxanthine

b- Deamination of Thymine into Uracil leads to transition mutation

c- AP site is produced by depurination

d- None of the above

e- A+B

Q21- All of the following are true about the semiconservative model , except :

a- The new duplex is formed of a strand from the parental duplex and a new

strand

b- DNA polymerase adds nucleotides to the free 5'-oh of the new strand

c- DNA polymerase can not add nucleotides de novo

d- Tranesterification involves a nucleophilic attack of the free 3'-oh on the 1st

phosphate of the added nucleotide

e- None of the above

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Q22- All of the following are functions of the single stranded DNA

binding proteins (SSB's) , except :

a- Keep the 2 strand apart to the prevent reannealing

b- Reduce potential secondary structures

c- Aligne template strands for rapid DNA synthesis

d- Associate with the sliding clamps

e- Have a role in recombination

Q23- All of the following are steps of the replication fork movement , except :

a- Primer synthesis by primase

b- Strand elongation by polymerase

c- Primer removal by RNaseH/FEN1

d- Gap filling by Okazaki synthetase

e- Sealing of the nick by ligase

Q24- One of the following is mismatched :

a- UV light pyrimidine dimmers

b- Carcinogens .. attack DNA

c- Spontaneous deamination U instead of C

d- Active oxygen species . O6- methyl guanine

e- Ionizing radiation .. break DNA strand

Q25- One of the following is wrong match :

a- Transition purine for a pyrimindine

b- Triplet expansion ... Huntington's disease

c- Photoreactivation .. repair of pyrimindine dimmers

d- Nucleotide excision repair . Removal of pyimindine dimmers

e- None of the above

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Elite Dental Team

Q26- Which of the following is responsible to sea nicks during DNA

replication :

a- DNA polymerase I

b- DNA polymerase II

c- DNA ligase

d- Primase

e- Telomerase

Q27- Which of the following functions is shared by pol I , pol II and pol III :

a- 5' 3' exonuclease

b- 3' 5' exonuclease

c- 5' 3' polymerization

d- A+B

e- B+C

Q28- Which of the following is responsible for mitochondrial DNA replication :

a- Pol segma

b- Pol alpha

c- Pol gamma

d- Pol epsilon

Q29- Thymine dimmer in DNA is caused by :

a- X-ray radiation

b- UV light

c- Free radicals

d- Deamination

THE END :)