33. DNA replication in prokaryotes and eukaryotes. DNA repairs. Flashcards

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1
Q

This process is “semi-conservative” (original strand acts as a template for the synthesis of the new DNA strand)

A

This process is “semi-conservative” (original strand acts as a template for the synthesis of the new DNA strand)

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2
Q

To begin DNA replication, DNA helices cause the two parent DNA strands to unwind to form a Y shaped replication fork. These replication forks are the actual site of DNA copying.

A

To begin DNA replication, DNA helices cause the two parent DNA strands to unwind to form a Y shaped replication fork. These replication forks are the actual site of DNA copying.

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3
Q

Single stranded DNA proteins bind to the single stranded DNA in replication fork. DNA primase joins and synthesises primers. After the primer is synthesised - DNA polymerase is attached. Nucleotides are joined by phosphodiester bonds.

A

Single stranded DNA proteins bind to the single stranded DNA in replication fork. DNA primase joins and synthesises primers. After the primer is synthesised - DNA polymerase is attached. Nucleotides are joined by phosphodiester bonds.

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4
Q

Prokaryotes: DNA polymerase I, II, III

Eukaryotes: DNA polymerase α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon)

A

Prokaryotes: DNA polymerase I, II, III

Eukaryotes: DNA polymerase α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon)

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5
Q

Elongation: synthesis of new DNA strand is in 5 -> 3 prime direction - leading chain replicates by DNA polymerase δ.
Lagging chain replicates by DNA polymerase ε Okazaki fragments 3 -> 5

A

Elongation: synthesis of new DNA strand is in 5 -> 3 prime direction - leading chain replicates by DNA polymerase δ.
Lagging chain replicates by DNA polymerase ε Okazaki fragments 3 -> 5

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6
Q

DNA repair: by DNA polymerases:

Prokaryotes - DNA polymerase I and II

Eukaryotes - DNA polymerase ε and δ

A

DNA repair: by DNA polymerases:

Prokaryotes - DNA polymerase I and II

Eukaryotes - DNA polymerase ε and δ

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7
Q

It’s was found that DNA polymerase III in E. coli adds wrong base every 10^4 base pairs

Rate of DNA repair depends on cell type, cell age, extracellular environment.

A

It’s was found that DNA polymerase III in E. coli adds wrong base every 10^4 base pairs

Rate of DNA repair depends on cell type, cell age, extracellular environment.

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8
Q

Apoptosis (programmed cell death), unregulated cell division, senescence - if damage is too much

Primer - serves as the start point of DNA synthesis - generally 10 base pairs. (strand of short nucleic sequences)

A

Apoptosis (programmed cell death), unregulated cell division, senescence - if damage is too much

Primer - serves as the start point of DNA synthesis - generally 10 base pairs. (strand of short nucleic sequences)

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9
Q

Initiation:

  • DNA helicases unwind strands in both directions + separate them by breaking its bonds between N-bases at origin of replication
  • replication fork formed, helix destabilising protein bind to prevent rejoining of strands
A

Initiation:

  • DNA helicases unwind strands in both directions + separate them by breaking its bonds between N-bases at origin of replication
  • replication fork formed, helix destabilising protein bind to prevent rejoining of strands
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10
Q

Elongation:

  • RNA primase added to template strand and synthesises RNA protein (with free 3’ OH group)
  • synthesis of new DNA strands always in 5’-3’ direction
  • Leading chain (5) extended by DNA polymerase δ
  • Lagging chain extended discontinuously by DNA polymerase III (prokaryotes) or ε (eukaryotes - Okazaki fragments
  • RNase removes primer RNA fragments, DNA pol I replaces RNA nucleotides with DNA nucleotides, DNA ligase binds fragments together
  • Topoisomers (I and II) need ATP, produce breaks in DNA and rejoin them to release stress during replication in the molecule
A

Elongation:

  • RNA primase added to template strand and synthesises RNA protein (with free 3’ OH group)
  • synthesis of new DNA strands always in 5’-3’ direction
  • Leading chain (5) extended by DNA polymerase δ
  • Lagging chain extended discontinuously by DNA polymerase III (prokaryotes) or ε (eukaryotes - Okazaki fragments
  • RNase removes primer RNA fragments, DNA pol I replaces RNA nucleotides with DNA nucleotides, DNA ligase binds fragments together
  • Topoisomers (I and II) need ATP, produce breaks in DNA and rejoin them to release stress during replication in the molecule
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11
Q

Termination:

  • replication continues until whole molecule covered
  • Telomerase removes primer at 5’ ends
  • Telomerase adds DNA repeating sequences (TTAGGG) to 3’ end in DNA strands in telomerase region
  • RNA to clone telomerase after every replication
  • termination site sequence in DNA + telomerase site binding proteins = termination at a certain locus
A

Termination:

  • replication continues until whole molecule covered
  • Telomerase removes primer at 5’ ends
  • Telomerase adds DNA repeating sequences (TTAGGG) to 3’ end in DNA strands in telomerase region
  • RNA to clone telomerase after every replication
  • termination site sequence in DNA + telomerase site binding proteins = termination at a certain locus
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12
Q

DNA repair:

  • Direct reversal - 3 types of damage eliminated by chemical reversal forms of pyrimidine dimers upon irradiation with UV radiation
  • SS damage - other strand can be used as template to guide correction of damaged strand
  • Base excision repair - damage to single or base. Repaired -> glycosylated -> all site
  • Nucleotide excision repair
A

DNA repair:

  • Direct reversal - 3 types of damage eliminated by chemical reversal forms of pyrimidine dimers upon irradiation with UV radiation
  • SS damage - other strand can be used as template to guide correction of damaged strand
  • Base excision repair - damage to single or base. Repaired -> glycosylated -> all site
  • Nucleotide excision repair
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