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Biol 243 Midterm > 1C > Flashcards

1C Flashcards

1
Q

Models of DNA replication

A
  1. Semi conservative (daughter + complimentary parental)
  2. Conservative (daughter+daughter)
  3. Dispersion (mix daughter and parent)
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2
Q

Meselson and Stahl goal

A
  1. Track parental and newly synthesize DNA over many generation with nitrogen isotope incorporated into DNA molecules through nitrogenous base (15N)

(Line test thing)

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3
Q

Where are nucleotides added for DNA synthesis

A

At 3’-OH so DNA synthesis occurs in 5’->3’ direction…

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4
Q

During DNA synthesis what provides E for the formation of new phosphodiester bonds

A

Hydrolysis of pyrophosphate

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5
Q

Properties of DNA poly

A

-synthesize new DNA in 5->3
-read template DNA strand in 3->5
-CANNOT synthesize from scratch needs RNA primer + 3’-OH for synthesis
-single active site catalyze 4 diff rxns (dATP, dCTP, dGTP,dTTP)

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6
Q

Replisome

A

Molecular machine of enzymes that replicates DNA

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7
Q

Helicase

A

Unwinds double helix by breaking h-bons

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8
Q

Primase

A

Synthesize RNA primer for DNA poly

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9
Q

Single strand binding protein

A

Stabilise ssDNA before replication… how? Prevent reannealing so strand can serve as template

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10
Q

DNA topoisomerase/gyrase

A

Remove super coil that form ahead of replication fork… relieve torque of mainly circular DNA

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11
Q

DNA poly III

A

Synthesize DNA by adding nucleotides to new DNA strand

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12
Q

DNA poly I

A

Remove RNA primer and fill gaps with DNA

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13
Q

Sliding clamp

A

Attaches DNA Pol III to DNA template…replication more efficient

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14
Q

DNA ligase

A

Join ends of DNA segments by forming phosphodiester bonds

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15
Q

Replication forks??

A

Site of DNA synthesis

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16
Q

Which strand is synthesized continuously and which is synthesized discontinuously during DNA replication

A
  1. lagging is discontinuous
  2. Leading is continuous (Okazaki fragments)
17
Q

DNA replication enzymes in order

A
  1. DNA helicase-unwind double helix
  2. RNA primase-put RNA primer
  3. Topoisomerase/gyrase- prevent twisting ahead of replication fork during unwinding
    4.DNA pol. III-extend RNA primer
  4. DNA helicase keepsunwinding leading and lagging strand by DNA Pol III
  5. DNA Pol I-removes RNA primer of Okazaki fragments and fill gap with dNTPs (deoxynucleotide triphosphate)
  6. DNA ligase-seal gap with phosphodiester bond
18
Q

DNA replication of bacterial chromosomes

A
  1. Initiation: unwind and separate 2 template DNA strands at oriC (origin of replication site)
    2.elongation: synthesis of 2 new DNA strands from template strands by DNA poly (simultaneous)
  2. Termination: DNA replication stop at termination site (circular) or at end of chromosome (linear)
19
Q

DNA replication of eukaryotic chromosome

A

-linear chromosome
-Multiple origin
-replication in opp. Direction (away from origin)
-end of linear chromosome has problem replicating

20
Q

PCR

A

Polymerase chain rxn (DNA replication and amplification in test tube)

21
Q

Issue replicating ends of linear chromosomes (end of replication probem)

A

-need RNA primer, why? Intimate new DNA synthesis so 3’end of linear chromosome replication is complicated
-no DNA poly can fill gap at chromosomal end=> additive loss at end
-gene at end of chromosome can be deleted….=> death of organism

22
Q

How do telomeres fix the end replication problem

A

-add noncoding ssDNA to 3’ end by telomerase
-telomeres worn away after each DNA replication/division
-if telomere region is gone=?cell stop dividing

23
Q

Telomerase?

A

Enzyme=>restore shortened teloemres

24
Q

Is telomerase in eukaryotic cells?

A

NOOO…=> short telomeres in old peep

Telomerase in gametes and stem cells (as get older, shorter telomeres cause less telomerase)

25
Q

HTERT

A

Gene mutation (human telomerase)=>biomarker in cancer

26
Q

DNA high fidelity…

A

-replicated fully
-no errors

… if not,
-> defective genome (and maybe death)

So,
DNA repair mechanism by enzyme complex lower replication error rate

27
Q

Telomere role in replication

A

Ensure ends of linear chromosomes are fully replicated

28
Q

Which way does DNA Pol III synthesize new strand

A

5->3

29
Q

DNA poly proofreading

A

-optimum conformation
-DNA pol III see mistake and uses 3->5 exonuclease to remove mismatched nucleotides and replace correct to contîntes synthesis in 5->3

30
Q

MMR

A

DNA mismatch repair

31
Q

Use of MMR

A

Cover replication errors not corrected by proofreading

32
Q

How does MMR work… process?

A
  1. recognize mismatch damage by DNA binding protein (MutS and MutL)…
  2. MutH endonuclease daughter strand away from mismatch
  3. Exo1 5’-3’ exonuclease excise region of daughter strand around mismatch
  4. DNA Pol III fills gap and repais mismatch
  5. Gap waged by DNA ligase

Biol 243 Midterm (8 decks)

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