33. DNA replication in prokaryotes and eukaryotes. DNA repairs. Flashcards
This process is “semi-conservative” (original strand acts as a template for the synthesis of the new DNA strand)
This process is “semi-conservative” (original strand acts as a template for the synthesis of the new DNA strand)
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.
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.
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.
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.
Prokaryotes: DNA polymerase I, II, III
Eukaryotes: DNA polymerase α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon)
Prokaryotes: DNA polymerase I, II, III
Eukaryotes: DNA polymerase α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon)
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
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
DNA repair: by DNA polymerases:
Prokaryotes - DNA polymerase I and II
Eukaryotes - DNA polymerase ε and δ
DNA repair: by DNA polymerases:
Prokaryotes - DNA polymerase I and II
Eukaryotes - DNA polymerase ε and δ
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.
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.
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)
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)
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
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
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
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
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
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
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
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
