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27 Cards in this Set
- Front
- Back
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Replication occurs only for ...
If it doesn't ..., there's no reason for it to replicate its DNA |
cell division
divide |
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DNA replication uses what kind of replication?
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semiconservative replication
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Eukaryotic replication has ... origins of replication, is ...-directional, and uses ... replication
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numerous
bi- semiconservative |
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The replication fork:
... → separates DNA strands and unwinds the parental duplex (allows enzymes access to DNA) ... → breaks and reforms phosphodiester bonds to relieve the supercoiling of the parental duplex caused by unwinding ... → prevent strands from reassociating and protect from enzymatic cleavage |
helicase
topoisomerase single-strand binding proteins |
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DNA synthesis:
-RNA primers (about 10 nucleotides in length) created by ... necessary to initiate synthesis of new strands -... adds nucleotides to the 3’-OH end of the growing strand → ... bond formation -new nucleotides forming the daughter strand are matched to the ... nucleotides on the parent strand (A::T and C:::G) |
RNA polymerase (primase)
DNA polymerase phosphodiester complementary |
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growth has to occur in the ... direction. Polymerase only works in this direction
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5' to 3'
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DNA polymerases:
at least 9 DNA eukaryotic DNA polymerases (α,β,γ,δ,ε,ζ,κ,η,ι) possess two enzymatic activities: -5’→3’ ... (synthesis) (forming new phosphodiester bonds) -3’→5’ ... activity (repair) (important in proofreading. detects mismatches) |
polymerization
exonuclease |
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-DNA synthesis along the ... (away from the replication fork) is discontinuous and requires multiple ...
-fragments are eventually joined together by ... -fragments are approximately the size of DNA found in ... (so likely that DNA released for replication is unwound one nucleosome at a time) |
lagging strand
RNA primers DNA ligase nucleosomes |
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RNA primers removed by ... and ...
gap left by primer is filled by ... |
RNase H
flap endonuclease 1 (FEN1) DNA polymerase |
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DNA ... joins fragments together
DNA ... fills in gaps |
ligase
polymerase |
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DNA ligase joins Okazaki fragments by forming a ... bond between two adjacent DNA strands that are bound to the same template
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phosphodiester
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prokaryotic replication:
one long, circular DNA strand ... origin of replication (... site) with 2 replication forks DNA replicated much more quickly than in eukaryotes (one million bp per minute vs. 500-5000 bp per minute) enzymes use different nomenclature |
single
ori |
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Replication can be targeted in the treatment of diseases, particularly ... and infectious diseases.
nucleotide ... commonly used -mechanism: inhibit DNA replication |
cancer
analogs |
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zidovudine (ZDV, or AZT)
-treatment of ... -analog of ... -stops DNA chain elongation (no 3’-OH, N3 instead) |
HIV/AIDS
deoxythymidine |
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what is this?
-chemotherapeutic agent -cancer treatment -not specific to just cancer cells -many adverse side effects -an analogue of uracil or thymine |
5-florouracil
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what are these?
-inhibit bacterial DNA gyrase (topoisomerase II), preventing DNA replication and transcription -used to treat aerobic gram-negative bacteria (gonorrhea, urinary tract infections) -nalidixic acid, ciprofloxacin, norfloxacin |
quinolones
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what is this?
-marker of replicating cells -utilized clinically to identify replicating and dividing cells in histological sections |
PCNA = Proliferating Cell Nuclear Antigen
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As DNA replication approaches the ends of chromosomes, one of two possible problems arise:
-... cannot lay down primer at very end of chromosome -the RNA primer at end of chromosome is ... Result: newly synthesized DNA strand (daughter strand) is shorter at 5’ end and there is a 3’-overhang in the DNA strand being replicated (parent strand) --> every time a cell replicates its DNA and divides, it ... small pieces of its chromosomes! |
primase
degraded loses |
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what is this?
-solution to "end replication problem" -repeating sequence of bases found at the ends of linear chromosomes -act as disposable buffers (small portion lost each time chromosome is replicated for cell division -also help cells distinguish ends of chromosomes (as opposed to chromosomal breaks) and prevent ends of chromosomes from joining together -like plastic tips of shoelaces -protects ends from damage/degredation |
telomeres
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In addition to repeating string of TTAGGG, telomeres contain:
... - enzyme that maintains telomeres during replication. Expression repressed in many cell types (blood cells, stem cells). activity decreases with age -... - template RNA used to rebuild telomere -... - loop or knot at the distal 300bp portion of the telomere that stabilizes end of chromosome |
Telomerase
Telomerase RNA component T-Loop |
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Role of telomeres in aging:
-Most somatic cells do not express telomerase. (exceptions: stem cells, white blood cells) -result is a gradual ... as cells divide (and as we mature into adults and “age”) -Cells have a built-in growth “stop-watch” or death “fuse” that ... the number of times they can divide. -Eventually, telomere shortening leads to cell ... (cessation of growth, inability to divide) or ... |
loss of telomeres
limits senescence cell death |
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What is the inability to repair or replace damage tissue?
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aging
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we age because cells can no longer ... their chromosomes and undergo successful cell division
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replicate
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uncontrolled cell division --> ...
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cancer
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when most cancer cells divide, they (do/do not) lose their telomeres (unlimited replication)
increased telomerase activity |
do not
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Cancer/tumor suppression --> block ... activity or shorten ... in cancer cells
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telomerase
telomeres |
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the big Trade-off:
prevent ... by preserving telomeres (cell survival) or increase vulnerability to ... |
aging
cancer |
