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DNA replication ppts Flashcards

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1
Q

what are examples of nucleic acids?

A

DNA/RNA

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2
Q

what are nucleic acids made up of?

A

polymers consisting of monomers (nucleotides)

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3
Q

what are nucleotides made of?

A

1) a pentose sugar
2) a phosphate group
3) a nitrogenous base

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4
Q

DNA replication is always _____ to _____

A

5’ to 3’

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5
Q

DNA is always read ____ to _____

A

3’ to 5’

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6
Q

Energy for formation of phosphodiester (sugar) bond is released by the breaking of the ______ bond.

A

triphosphate

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7
Q

The ____’ (prime) end of the free nucleotide is added to the ____’ (prime) end of the nucleotide chain that is already formed.

A

5, 3

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8
Q

We talk about DNA being double stranded and aligned in an anti-parralel orientation.

Does this mean that both strands of DNA are identical to each other?…

A

no, they are complimentary

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9
Q

how many bonds between A and T?

A

2

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10
Q

How many bonds between G and C?

A

3

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11
Q

Explain basic steps associated with DNA replication
Precursors, enzymes, direction
Specifically the need of a RNA primer

A
  • DNA replications is initiated by RNA primer
  • DNA is copied by DNA polymerase
  • Leading strand is synthesized continuously
  • lagging stand synthesized in Okazaki fragments
  • RNA primers are removed and Okazaki fragments are joined by DNA ligase
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12
Q

Explain when/where does DNA replication occur in prokaryotes? In eukaryotes?

A

multiple origin of replication in eukaryotes

only one OR in prokaryotes

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13
Q

Which chromosomal features are essential to both bacterial and eukaryotic chromosomes?

A

origin of replication

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14
Q

The origin of replication in eukaryotes is at ____ locations next to _____ genes

A

defined, important

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15
Q

What is meant by bidirectional replication?

A

in prokaryotes, the origin of replication is bidirectional, meaning it has two replication forks

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16
Q

in what direction is the leading strand going?

A

3’ to 5’ (toward the fork)

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17
Q

in what direction is the lagging strand going?

A

5’ to 3’ (away from fork)

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18
Q

what is the purpose of helicase?

A

binds to double stranded DNA and breaks the hydrogen bonds between the nucleotides, separating the strands

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19
Q

what does unwinding cause?

A

unwinding induces supercoiling ahead of the replication fork

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20
Q

what is the purpose of DNA topoisomerase?

A

to break DNA and allow it to uncoil, then reseal the break

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21
Q

what first imitates replication?

A

RNA primer - polymerase will not synthesize without it

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22
Q

How long is an RNA primer? How is it made?

A

5-10 bases long, primes

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23
Q

why use RNA?

A

If there is a mistake, when DNA is added back into it to make a new strand, the body will notice an error and fix it

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24
Q

how often is there an origin of replication in linear DNA?

A

every 3000 bp

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25
Q

What is the problem with the replication of linear DNA.

A

Removal of the RNA primer at the end will leave a 3’ overhang

  • this leaves a gap from RNA removal at tellers because no new DNA synthesis could fill them in
26
Q

Telomerase

A

ribonucleoprotein (made of RNA and Proteins) “TTAGGG”

27
Q

Which of the following is analogous to telomeres?

A

the two ends of a shoelace

28
Q

In what type of cell would you expect to normally see telomerase activity

A

Embryonic Cells

29
Q

What components are needed to replicate DNA?

A 
A. Free Nucleotides (ATP, GTP, CTP, TTP)
B. Primers to direct DNA polymerase
C. DNA polymerase
D. Template DNA
E. All of the above are needed

E

30
Q

What are the necessary components of PCR reactions?

A

The various components required for PCR include a DNA sample, DNA primers (oligonucleotides), free nucleotides called ddNTPs, and DNA polymerase.

31
Q

Why must the DNA polymerase be highly thermally stable?

A

because during PCR, temperature rise and fall for denaturing, annealing, and synthesis. That is why helicase isn’t used in PCR

32
Q

What are some advantages and limitations of PCR?

A

amplifies a lot of DNA

33
Q

oligonucleotides

A

short pieces of synthetic DNA can be manufactured that contain any sequence,

…template specific!

34
Q

How is DNA strands separated in PCR

A

heat

35
Q

why can’t you use helicase in vitro?

A

…DNA denaturing conditions such as high heat or low salt concentrations irreversibly denature or inactivate most polymerases,

…dNTPs are not affected by denaturation,

…primers are not affected by denaturation.

36
Q

What are the temperatures of the thermal cycle, and what steps occur at each of these temperatures?

A

94 degrees - Denature

60 degrees - Anneal

72 degrees - Synthesis

37
Q

Exponential synthesis requires:

A

as few as 1 DNA templates required,

excess dNTPS,

excess primers,

multiple cycles.

38
Q

DNA helixes run ____

A

anti-parallel

39
Q

What is the correct model for DNA replication?

A

semi-conservative model

40
Q

how many origin of replications do bacteria have?

A

1, but they have two replication forks - the forks run in opposite directions (bidirectional)

41
Q

what initiates replication in bacteria?

A

binding of DnaA proteins

42
Q

where is bacterial DNA first separated?

A

AT rich region, separated by helicase

43
Q

what all is needed for linear DNA replication?

A

RNA primer, helicase, topoisomerase, single stranded binding proteins, DNA polymerase III and I, DNA ligase

44
Q

DNA helicase

A

breaks hydrogen bonds

45
Q

Topoisomerase II

A

alleviates positive supercoiling

46
Q

Single stranded binding proteins

A

keep the parental strands apart

47
Q

Primase

A

synthesis RNA primer

48
Q

RNA primer

A

initiates replication - 10-12 bp in length

49
Q

DNA polymerase III

A

synthesizes new strand of DNA

50
Q

DNA polymerase I

A

knocks off RNA primers and fills in their gaps with DNA

51
Q

DNA ligase

A

covalently links the Okazaki fragments together

52
Q

what are dNTPs?

A

deoxiribonucleotiside triphosphate (nucleotides)

53
Q

what removes mismatched bases?

A

an exonuclease on the 3’ end of the DNA polymerase

54
Q

in eukaryotes, what gets rid of RNA primers on lagging strand?

A

Flap endonuclease, removes flaps created by DNA squiggle

  • cannot remove a flap if its too long
55
Q

the ends of eukaryotic chromosomes are replicated by

A

telomerase

56
Q

how does telomerase work?

A

additional DNA sequences are attached to the ends of telomeres, where telomerase recognizes the sequences and synthesizes additional repeats of telomeric sequences

57
Q

what is the problem with telomerase?

A

activity of telomerase decreases with age

58
Q

what are the steps of telomerase?

A

1) binding to the 3’ overhang
2) polymerization - telomerase synthesizes a new 6 nucleotide repeat
3) moves 6 nucleotides to the right to make another sequence (translocation)
4) complimentary strand is made by primate, polymerase, and ligase

59
Q

what part of telomerase contains the sequence complimentary to the telomeric repeat sequence?

A

TERC - telomerase RNA component

60
Q

telomerase reverse transcriptase (TERT)

A

uses RNA template to synthesize DNA

Genetics (12 decks)

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