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Genetics 380 > DNA Replication > Flashcards

DNA Replication Flashcards

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1
Q

speed of DNA replication

A

fast; takes a few hours to replicate 3.3 billion bp of human DNA

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2
Q

mistakes in DNA replication

A

have 3’ to 5’ exonuclease activity that enables to proofread and fix mistakes; DNA repair proteins that can replace incorrectly placed nucleotide; these features bring error rate to 1 per 1 million nucleotides

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3
Q

conservative replication

A

original DNA molecule stays intact and completely new molecule is synthesized

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4
Q

dispersive replication

A

original DNA molecule gets fragmented & fragments used as templates for synthesis of new DNA then the chromosomes get reassembled; resultant chromosomes have old & new DNA scattered throughout both strands

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5
Q

semiconservative replication

A

original DNA molecule unwinds & each strand is used as template for synthesis of new strand; resultant chromosomes have one old strand and one new strand

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6
Q

Meselson and Stahl

A

demonstrated that DNA replication is semiconservative

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7
Q

Meselson and Stahl experiment

A

grew DNA molecules in nitrogen isotopes of different weights: after 2 rounds of some DNA was light and some was intermediate suggesting semiconservative replication

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8
Q

Taylor

A

confirmed semiconservative replication in eukaryotes

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9
Q

Taylor experiment

A

bean root tips & radioactive tritium; one round mitosis: both sister chromatids labelled; 2 rounds of mitosis: only one sister chromatid from each chromosome labelled

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10
Q

theta replication

A

in organisms w circular chromosomes (bacteria); double helix unwinds at single origin of replication creating replication bubble w replication fork at each end; replication proceeds in both directions

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11
Q

rolling circle replication

A

viruses & plasmids; one DNA strand cut to 5’ phosphate end and 3’ OH end; new nts added to 3’ end using intact other strand as template as new DNA strand elongates it pushes 5’ end of cut strand off other strand; old strand cleaved off other strand & circularizes and is used as template for replication ending w two circular DNA molecules

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12
Q

replicating linear chromosomes

A

many origins of replication - replication in both directions; each replication bubble produces one replicon

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13
Q

order of events in DNA replication

A

initiator protein/complex recognizes origin of replication; helicase unwinds double helix separating 2 DNA strands; single strand binding proteins keep 2 DNA strands from reannealing; topoisomerase nicks one strand of DNA in regions just outside rep forks to release tension caused by unwind tightly coiled DNA mol - so cell can cont to open double helix and replicate all its DNA; primase lays down primer that contain RNA nucleotides; DNA polymerase uses DNA strand as template & synthesizes complementary strand; DNA polymerase removes RNA primers and replaces them w DNA nucelotides; DNA ligase knits all pieces together: DNA frags that replaced RNA primers, stretches of DNA between primers, Okazaki fragments

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14
Q

origin of replication

A

OriC; has characteristic repetitive seq (rich in A/Ts) that varies a bit from species to species

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15
Q

origin recognition complex (ORC)

A

in eukaryotes ORC binds to origin of rep and causes replication licensing factor (RLF) to bind there as well; RLF attaches to origin of replication and unwinds a little of the helix allowing DNA rep to begin

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16
Q

DNA helicase

A

opens helix up to expose the bases which creates replication bubble w replication forks at either end

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17
Q

single stand binding proteins

A

hold helix open

18
Q

topoisomerase I

A

breaks DNA strand outside open region in eukaryotes allowing strands to pass through each other then close the break; if tension doesn’t get relieve helix will not be able to open up very far & most of the DNA will not be accessible to replication machinery

19
Q

4-quinoline antibiotics

A

(ex: ciprofloxacin) kill bacteria by inhibiting gyrase the topoisomerase used by bacteria

20
Q

DnaG

A

lays down stretch of 10-12 RNA nucleotides (ribonucleotides) in bacteria

21
Q

DNA polymerase alpha

A

lays down primer in eukaryotes; primer is mad of RNA & DNA - consists of approx 10-12 ribonucleotides plus approx 23-30 deoxyribonucleotides

22
Q

DNA polymerase delta

A

replicates lagging strand in eukaryotes

23
Q

DNA polymerase epsilon

A

replicates leading strand in eukaryotes (DNA polymerase III does this in bacteria)

24
Q

replication protein A (RPA) & DNA polymerase delta

A

remove primers in eukaryotes; RPA unwinds DNA/RNA hybrid causing one end of primer to stick out like loose flap and binds to loose flap of RNA to keep it from reannealing

25
Q

endonuclease

A

recruits by RPA to cut at other end of primer removing primer DNA polymerase delta then fills in gap w DNA nucleotides (DNA polymerase I does this in prokaryotes)

26
Q

DNA ligase

A

knits diff frags together: DNA frags that replaced RNA primers, stretches of DNA between primers, Okazaki frags

27
Q

leading strand

A

replicated continuously to the end of chromosomes or to next rep fork whichever comes first; DNA polymerase can only add to 3’ end

28
Q

lagging strand

A

synthesized in fragments of approx 1500 nucleotides (Okazaki fragments)

29
Q

eukaryotes & telomeres

A

cannot replicate telomeres; length of telomeres regulates lifespan of eu cell = when telomeres reach certain length cell goes into apoptosis

30
Q

telomerase

A

RNA protein complex that fills in telomeres; in human only active in few cell types ex: gametes or B cells of immune system; RNA portion of telomerase binds to DNA & acts as template for new synthesis; protein portion synthesizes new DNA to fill in telomere

31
Q

telomerase inhibitors

A

help battle cancers that are caused by gain of function mutation in telomerase

32
Q

Werner syndrome

A

premature aging syndrome; defect in RecQ helicase: enzyme that is essential for telomere replication

33
Q

histone chaperone proteins

A

help assemble histones into 8 histone cluster

34
Q

chromatin assembly factor 1 (CAF1)

A

helps assemble DNA back into proper configuration

35
Q

replication licensing factor (RLF or MCM)

A

to avoid duplicate rep; contains several proteins including helicase and protein geminim; RLF attaches to origin of replication & unwinds little of the helix allowing DNA replication to begin

36
Q

geminim

A

present on origin of rep prevents another RLF from attaching; degraded in G1 so DNA rep can reoccur in next S phase

37
Q

ter sites

A

signal termination of replication

38
Q

tus (terminus utilization substance) protein

A

binds to one of the ter sites and stops one of the rep forks allowing other fork to come and meet it

39
Q

topoisomerase II

A

forms double stranded break in DNA allowing 2 circular DNAs to become untangled so they can migrate into 2 daughter cells when cell splits

40
Q

avoiding duplicate rep in prokaryotes

A

tus protein and ter sites

Genetics 380 (11 decks)

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