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Life Science 3 > L5: DNA Replication > Flashcards

L5: DNA Replication Flashcards

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Biology 101 flashcards
1
Q

Eukaryotic Cell Cycle

A
  • S phase or DNA Replication
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2
Q

Replication

A
  • carefully regulated by the timing of the cell cycle and critical cell cycle “checkpoints”
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3
Q

Watson-Crick semiconservative hypothesis

A
  • one of each parental DNA strands will be present in each of the two newly synthesized daughter dsDNA
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4
Q

conservative vs. semiconservative DNA replication

A
  • conservative:
    • both parental DNA strands are conserved in the daughter DNA
  • semi-conservative:
    • only one of the two parental strands is conserved in the daughter dsDNA
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5
Q

Conservative DNA replication

A
  • both parental DNA strands are conserved in the daughter DNA
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6
Q

Semiconservative DNA

A
  • only one of the two parental strands is conserved in the daughter dsDNA
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7
Q

DNA replication is ______

A

semi-conservative

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8
Q

5 Features of DNA replication

A
  1. DNA replication starts from a replication origin
  2. DNA replication is a DNA template-dependent polymerization process that needs RNA primers
  3. DNA synthesis is always 5’-3’, so replication of dsDNA has to process in opposite directions (bidirectional replication)
  4. DNA is synthesized continuously (leading strand), as well as discontinuously (lagging strand-synthesized as Okazaki fragments)
  5. DNA replication is very accurate and fast
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9
Q

Direction of DNA synthesis is ______

A
  • 5’-3’

- the 3’ hydroxyl group of the existing DNA is where the incoming nucleotide will be added

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10
Q

DNA synthesis

A
  • substrates: Deoxyribonucleoside triphosphates

- chemistry: 3’ OH attacks phosphate on incoming nucleoside triphosphate

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11
Q

Origin of replication

A
  • prokaryote:
    • there is one single origin per genome (or plasmid), also called a replicon
  • eukaryote:
    • have multiple origins in each chromosome (10,000 in human genome)
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12
Q

The parental dsDNA needs to be opened to become two ssDNA at the _____ _____

A

replication origin

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13
Q

Replication of a circular bacterial DNA occurs from _____ _____

A

one origin

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14
Q

In _____, there are many origins of replication per chromosome

A

eukaryotes

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15
Q

DNA replication is _____

A

bidirectional

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16
Q

DNA replication is bidirectional

A
  • REPLICATION FORK
    • the place where dsDNA “melts” into two ssDNA, there are 2 forks per origin
    • replication process at both ends of the replication fork
  • LEADING STRAND
    • strand that is synthesized continuously
  • LAGGING STRAND
    • strand that is synthesized discontinuously, resulting in Okazaki fragments
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17
Q

Replication fork

A
  • the place where dsDNA “melts” into two ssDNA, there are 2 forks per origin
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18
Q

Leading strand

A
  • strand that is synthesized continuously
19
Q

Lagging strand

A
  • strand that is synthesized discontinuously, resulting in Okazaki fragments
20
Q

Since DNA synthesis is always 5’, one daughter strand is synthesized _____ and the other is synthesized _____

A

continuously, discontinuously

21
Q

Consequences of replication fork structure

A
  • one DNA strand (leading strand) grows continuously
  • one strand (lagging strand) is synthesized in short pieces (Okazaki fragments) that must be joined together
  • DNA lagging strands must be initiated repeatedly by RNA priming (primase can initiate an RNA chain)
22
Q

Key enzymes and accessory proteins involved in DNA replication

A
  • helicase
  • DNA topoisomerase
  • primase
  • DNA polymerase
  • RNase H
  • DNA Ligase
  • ssDNA binding protein (SSB)
  • sliding clam protein
23
Q

_____ unwinds dsDNA to create ssDNA

A

Helicase

24
Q

Unwinding of the double helix at replication fork causes _____ of the DNA helix

A

supercoiling

25
Q

DNA topoisomerase

A
  • removes supercoils by creating a transient break in one or two strands of DNA, which releases the tension and allow DNA to return to normal helix (10bp per turn)
26
Q

_____ is an RNA polymerase

A

Primase

27
Q

Primase

A
  • an RNA polymerase

- synthesizes short RNA primers (5-10 nucleotides long) to help the initiation of DNA replication

28
Q

SSB

A

single strand DNA binding protein

29
Q

SSB

A
  • bind and stabilize ssDNA
30
Q

DNA polymerase

A
  • both prokaryotic and eukaryotic cells have multiple DNA polymerases
  • DNA polymerase III is the major E. coli DNA replication enzyme
    • has 3 major enzyme activities
31
Q

Major enzyme activity of DNA polymerase

A
  1. 5’ -> 3’ polymerase activity–for SNA synthesis
  2. 5’ -> 3’ exonuclease activity–for removal of RNA primers
  3. 3’ -> 5’ exonuclease activity–for repairing mistakes
32
Q

RNase H

A
  • specifically degrades RNA in the RNA:DNA hybrid

- removal of the RNA primer by RNase H and the 5’-3’ exonuclease activity of DNA polymerase

33
Q

DNA ligase

A
  • creates a phosphodiester bond between an adjacent 5’ phosphate and 3’ OH
  • fills the gaps between Okazaki fragments to make a continuous DNA molecule
34
Q

Sliding clamp protein (Beta clamp)

A
  • helps polymerase to bind to the template strand rapidly after each round of lagging strand synthesis
35
Q

Proof reading

A
  • DNA polymerase has proofreading function (3’-5’ exonuclease activity), which allows it to detect mistakenly incorporated nucleotides, remove them, and replace with the correct nucleotides
  • good but not perfect, reason for “spontaneous” mutations in the genome and why organisms have kept evolving
36
Q

Summary: DNA is synthesized in a _____ manner

A

semi-conservative

37
Q

Summary: DNA is synthesized _____

A

bidirectionally

38
Q

Summary: At each replication fork, DNA is synthesized continuously on the _____ strand and discontinuously on the _____ strand

A

leading, lagging

39
Q

Summary: _____ is used as primer

A

RNA

40
Q

Summary: RNA primer is removed later and replaced by _____

A

DNA

41
Q

Cancer

A
  • accumulation of multiple mutations in two types of genes and the break-down of regulatory mechanisms of cell growth
  • two types of genes involved in cancinogenesis are: oncogenes and tumor suppressor genes
  • mutation in both the proto-oncogene and tumor suppressor gene are usually needed to cause cancer in which also why it is so difficult to treat cancer
  • tumor suppressor genes are genes for which the loss of function causes cancer.
  • can encode transcription factors cell-cycle regulators,phosphates, etc…
  • tumor suppressor gene products are so often inhibitors of cell proliferation
42
Q

Two types of genes involved in cancinogenesis are:

A

oncogenes and tumor suppressor genes

43
Q

_____ _____ genes are genes for which the loss of function causes cancer.

A

tumor supressor genes

44
Q

tumor suppressor gene products are so often inhibitors of ____ _____

A

cell proliferation

Life Science 3 (9 decks)

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