Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBG 2040 > DNA replication > Flashcards

DNA replication Flashcards

1
Q

the central dogma of biology

A

DNA to RNA = transcription
RNA to protein = translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

importance of DNA replication

A
  • ensures an exact copy of the species’ genetic info is passed from cell to cell
  • if DNA failed to replicate itself meiosis and mitosis would pause
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

features of DNA structure

A
  • right-handed and asymmetrical
  • complimentary base pairs (A with T and G with C)
  • 10 base pairs per turn
  • 0.34 nm between stacked basses and 3.4 nm per helical turn
  • anti-parallel 5’ to 3’ strands
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why do AT and GC pair

A
  • the space between ladders can only fit 3 rings
  • A and T are able to make 2 H-bonds
  • C and G are able to make 3 H-bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

semi-conservative copying mechanism

A
  • after one round of DNA replication each DNA contains 1 parental and 1 newly-synthesized strand
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

conservative replication

A
  • after first replication one new and one parental strand
  • after second replication one parental and 3 new strands
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

dispersive replication

A

nothing is conserved
- after first replication 2 half strands
- after second replication 4 half strands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

semiconservative replication products

A
  • after first replication 2 half strands
  • after second replication 2 half strands and 2 new strands
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Meselson and Stahl experiment

A

used cesium chloride equilibrium-density gradient centrifugation to separate double-stranded DNA molecules of different densities
- heavier DNA sediments near bottom and lighter ones near the top
- concluded that DNA replication in E. coli is semiconservative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Theta replication

A
  • replication that occurs in most circular DNA (bacterium)
  • replication is bidirectional
  • unwinding at replication origin produces single-stranded templates (making a replication bubble) with replication forks at the end proceed around the circle
  • eventually 2 circular DNA molecules are produced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

rolling circle replication

A
  • occurs on the F factor of some viruses
  • replication is unidirectional
  • break in a nucleotide strand causes DNA synthesis to begin at 3’ end of the broken strand, inner strand is used as the template, 5’ broken end is displaced
  • cleavage releases a single-stranded linear DNA (which may circularize) and double-stranded circular DNA
  • products are multiple circular DNA’s
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Linear chromosome replication

A
  • occurs in the linear chromosomes of eukaryotic cells
  • replication is bidirectional
  • numerous origins of replication where DNA unwinds producing a replication bubble
  • DNA synthesis takes place on both strands at each end of the bubble, replication fork proceeds outward and eventually reaches another where DNA segments will fuse
  • product is 2 identical linear DNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

RNA primase

A

helps DNA polymerase
- synthesizes a bit of RNA where you want DNA polymerase to start and contains an -OH group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

DNA replication requirements

A
  • magnesium (Mg2+)
  • DNA dependent DNA polymerase
  • 4 dNTPs
  • a template DNA to be copied
  • an RNA primer (provides 3’-OH end to initiate DNA synthesis by DNA polymerase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

features of DNA replication

A
  • always synthesized 5’ to 3’
  • ## newly synthesized strand is complementary and anti-parallel to parent strand
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how is new DNA synthesized from dNTPs

A
  • 3’-OH group of the last nucleotide on the strand attacks the 5’ phosphate of the incoming dNTP
  • two phosphates are cleaved off and a phosphodiester bond forms between the 2 nucleotides
  • the last incorporated nucleotide bonds with the alpha phosphate of the incoming nucleotide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

DNA chains and nuclease cleavage

A
  • single and double-stranded DNA is susceptible to cleavage by nucleases
  • chain cleavage can leave the alpha phosphate group attached to the 5’ or 3’ carbon of the sugar
18
Q

leading strand

A
  • continuous DNA synthesis
  • helices and polymerase are moving in the same direction so the polymerase doesn’t need to pause
19
Q

lagging strand

A
  • discontinuous DNA synthesis
  • made in segments since the polymerase needs to wait for another section of the DNA to get unwound by helicase
20
Q

DNA synthesis on leading and lagging strands

A
  • DNA synthesis proceeds 5’ to 3’, same direction as unwinding
  • on lagging strand, synthesis proceeds in the direction opposite of unwinding and runs out of template. it starts again, each time proceeding away from the replication fork which creates Okazaki fragments
  • on the leading strand, synthesis proceeds in the same direction as unwinding making one long strand
21
Q

replication fork

A

where the helices unwinds the DNA and the polymerase follows it

22
Q

what makes the rolling circle model of replication different from the others

A
  • replicates one strand at a time and doesn’t make a replication bubble
  • no lagging strand because polymerase and helicase go the same way
23
Q

origin of replication: theta model

A
  • DNA unwinds at the origin
  • at each fork synthesis of the leading strand proceeds continuously
  • synthesis of the lagging strand proceeds discontinuously
24
Q

origin of replication: rolling circle model

A
  • continuous DNA synthesis begins at 3’ end of broken nucleotide strand
  • as the DNA molecule unwinds, the 5’ end is progressively displaced
25
Q

origin of replication: linear eukaryotic

A
  • at each fork the leading strand is synthesized continuously in the same direction of unwinding
  • the lagging strand is synthesized discontinuously in the direction opposite of unwinding
26
Q

proteins involved in prokaryotic DNA

A
  • one 13-base pair tandem sequence (AT rich - easier to separate than GC)
  • four 9-base pair initiation protein binding sites
27
Q

priming of oriC

A
  • initiator proteins (DnaA) bond to ori C, the origin of replication causing small stretch of the DNA to unwind
  • unwinding allows helicase and other single-stranded-binding proteins to attach to the single-stranded DNA
28
Q

DNA helicase in prokaryotic replication

A
  • helicase unwinds the DNA 5’ to 3’ and travels on the lagging strand breaking H-bonds and moving the replication fork
  • unwound single-stranded DNA is coated with single-stranded binding protein to keep it single-stranded
29
Q

true or false: no DNA has free ends

A

true

30
Q

DNA gyrase

A

-released the stress caused by helicase by cutting one strand and letting it unwind a bit and wind back up again so it doesn’t create tension as the replication bubble gets bigger

31
Q

what happens when there is more positive supercoiling

A

more resistant the strand becomes yo being unwound

32
Q

DNA primase

A

synthesizes short RNA primer that provides the 3’-OH end for DNA polymerase to begin synthesis
- leading strand started first followed by lagging strand

33
Q

5 DNA polymerases in E.coli

A

1 and 3: chromosomal DHA replication
2,4 and 5: DNA repair functions

34
Q

replicative polymerases in prokaryotes

A

Pol 1:
- aids removal of RNA primers
- short tract synthesis
- has 5’ to 3’ and 3’ to 5’polymerase and exonuclease activity
- proofreading 5’ to 3’ exonuclease activity
Pol 3:
- main replicative polymerase
- highly processive (synthesizes lots of reactions without pausing)
- has 5’ to 3’ polymerase activity
- proofreading 5’ to 3’ exonuclease activity

35
Q

beta sliding clamp

A

a ring-shaped polypeptide that encircles the DNA and interacts with DNA polymerase 3 to enhance processive DNA synthesis
- helps keep polymerase on the DNA

36
Q

lagging strand and DNA polymerase

A

when Pol3 reaches 5’ end of the RNAprimer Pol3 is swapped for Pol 1
- Pol1 removes the RNA primer and resynthesizes a short tract DNA

37
Q

Elongation of DNA during replication in prokaryotes

A

-Pol 3 completes one Okazaki fragment then moves to initiate DNA synthesis of a new one
- in the mean time Pol 1 exchanges places with Pol 3 to remove RNA primers
- DNA must form a loop so both strands can replicate simultaneously

38
Q

All proteins involved in prokaryotic DNA replication

A
  • topoisomerase (gyrase)
  • helicase
  • single-stranded binding protein
  • DNA primase
  • DNA polymerase III (and beta clamp)
  • DNA polymerase I
  • DNA ligase
39
Q

What makes eukaryotic chromosome replication unique?

A
  • shorter RNA primers and Okazaki fragments
  • replication only occurs in the S phase
    -multiple polymerases (at least 15)
  • bidirectional replication from multiple origins on each chrom.
  • nucleosomes that need to be removed from parental DNA and re-assembled onto new DNA
    -telomeres: shorten at each round
40
Q

telomeres

A

protect the ends of chromosomes from degradation

41
Q

what is the problem with telomeres and eukaryotic DNA replication

A
  • the chromosome end will be degraded causing chromosome shortening every round
  • we can’t put a primer right at the end of DNA since telomere is there and primate needs to sit on chromosome
42
Q

how does replication happen on linear DNA with telomeres

A
  • the terminal primer is positioned 70-100 nucleotides from the end of the chromosome which leaves a gap that is not replicated

MBG 2040 (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions