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14 Cards in this Set
- Front
- Back
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Define the requirements for DNA synthesis |
1. DNA must be replicated identically before each division |
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Identify the key components of DNA Replication |
* DNA polymerases
* Primase * Helicase * Single stranded DNA binding complex protein * DNA topoisomerases * Clamp loading complex * DNA polymerase clamp |
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Recognize the function of the key components in DNA replication
[DNA Polymerases] |
Enzymes that catalyze the synthesis of DNA - 15 in total in eukaryotes - Polymerase δ, ε (major) & α involved in rep
Can only synthesize in the 3' --> 5' direction
Involved in multiprotein complex that binds near replication fork |
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Recognize the function of the key components in DNA replication
[DNA Polymerase α ] |
Starts DNA replication by binding with DNA primase
Lays down ~ 20 deoxyribonucleotides then dissociates
Has low processivity & no proofreading ability |
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Recognize the function of the key components in DNA replication
[DNA Polymerase ε] |
Follows DNA pol α in leading strand synthesis and continuously adds deoxyribonucleotides
Has high processivity and proofreading ability |
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Recognize the function of the key components in DNA replication
[DNA Polymerase δ] |
Follows DNA pol α in lagging strand synthesis
Adds deoxyribonucleotides until it reaches the start of the previous Okazaki fragment
Has proofreading abilities |
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Recognize the function of the key components in DNA replication
[Primase] |
Associates w/ DNA pol α in both leading and lagging strand synthesis
Lays down RNA primer containing base paired nucleotide w/ free 3' OH group
- Does this 1 for leading strand synthesis
lagging strand synthesis |
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Recognize the function of the key components in DNA replication
[Single Stranded DNA Binding Complex Protein] |
Bind to single stranded DNA after helicase activity
Prevents the ssDNA from base-pairing w/ itself (creating hairpin turns)
Straightens parent chain to facility DNA polymerase activity |
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Recognize the function of the key components in DNA replication
[DNA Topoisomerase] |
Preceeds all other replication proteins
Functions to relax backbone of DNA structure
Facilitates helicase activity afterwards |
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Recognize the function of the key components in DNA replication
[DNA Clamp Loading Complex] |
aka replication factor C-RPC
Facilitates attachment of bipartite DNA clamp to both leading and lagging strands
Hydrolyzes ATP to do so
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Recognize the function of the key components in DNA replication [DNA Polymerase Clamp] |
aka proliferating cell nuclear antigen (PCNA)
Bipartite structure forms large ring around DNA helix
One side binds to the back of DNA pol
Slides freely along helix as DNA pol moves
Bound tightly to DNA pol on leading strand
On lagging strand DNA pol dissociates when it reaches 5' end of previous Okazaki fragment - new clam forms at primer of next Okz frag
Ensures old template and newly synthesized strand remain together |
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Identify the differences between the synthesis of DNA in the leading and lagging strand |
Leading strand: after Pol α dissociates and Pol ε attaches, replication is continuous until replisome meets another replication bubble or it reaches the end of the helix
Lagging Strand: since synthesis can only proceed in 3'-5' direction, Okazaki fragments form that must be resolved through use of special DNA repair system - lagging strand folds back on itself facilitating loading of clamp - clamp and Pol stay in place |
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Identify the differences between the synthesis of DNA in the leading and lagging strand
[Okazaki Fragment Resolution] |
Special DNA repair system erases RNA primer and replaces it w/ DNA - Primer is removed by flap endonuclease 1 (FEN1) and RNAase H - Pol δ uses parental strand as template and free 3'-OH group from prev Okzaki fragment as a primer - DNA ligase joins 3' end of new DNA fragment to 5' end of previous one |
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Identify the differences between the synthesis of DNA in the leading and lagging strand
[Telomerase and the Lagging Strand] |
Telomeres are repetitive sequences at the end of chromosomes that prevent fusion of chromosomes and loss of vital DNA during replication
Newly synthesized lagging strand DNA is short on the 5' end; parent DNA strand has 3' over hang
Telomerase binds to 3' end of parent strand and extends it - Primase now binds and polymerase can synthesize remaining DNA onto daughter 5'-3' strand - Extra 3'-5' overhand complexed with telomere proteins |
