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22 Cards in this Set
- Front
- Back
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why do cells divide?
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-repair damaged tissue
-growth/development -replace old cells |
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must genetic material be replicated precisely during replication?
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yes
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define a mutation
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any permanent change to the DNA sequence
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do the consequences of germ line mutations differ from somatic cell mutations?
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yes
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what are the 5 requirements of DNA synthesis?
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primer, template, dNTPs, polymerase, divalent cations
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in DNA synthesis, does addition happen at the 3' end or the 5' end? why?
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3' because the 3' provides a free OH
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which 'direction' does DNA grow in?
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5'--->3'
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Why do cells dividE?
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-growth
-repair damaged tissue -replace old cells |
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is the mutation rate constant?
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yes
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how do enzymes that add nucleotides know which dNTP to add?
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complementary base pairing
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what type of replication does DNA go through? (Conservative, semi-conservative, or distributive)
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semi-conservative
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explain meselson and stahl's experiment and what it proved
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bacteria was grown in N-15 (heavy) and allowed to replicated, then it was grown in N-14 and centrifuged. in the first round of replication all the DNA went to the middle. In the 2nd round of replication, the bacteria went to the middle and the top. (Because heavy DNA went to the bottom)
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what are five things DNA synthesis requires?
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template, primer, dNTP, divalent cations, DNA polymerase
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what happens in a nucleophillic substitution?
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3' OH attacks the alpha phosphoryl group of dNTP, and the H bonds with P, so 2 Ps are released and the H is lost and O and P are left over = phosphodiester bond
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what ensures that DNA synthesis only goes from 5' to 3'?
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pyrophosphate molecule is released and immediately broken down so there's no possibility of a backwards reaction
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what does polymerase do?
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-holds base pairs in place
-maintains chemical environment -ensures correct bp -proofreads |
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describe the 3 regions of DNA polymerase
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palm (active site, proofreading)
thumb (stabilize primer/ increase processivity) fingers (grip dNTP and 90 degree bend of strand so only one base pair is in the active site at once) |
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why don't eukaryotes replicate straight down?
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it would take too long; need multiple replication bubbles
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where does the replication bubble open
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replication origin
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describe the discovery of okazaki fragments and why they are short
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okazaki labeled them with radioactive thymine and ran the DNA through a gel, and the shorter pieces were marked with thymine
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what's the benefit of DNA polymerase dissociating from DNA easily?
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DNA polymerase needs to de-attach to go back for the other parts of the lagging strand
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what are the 3 steps of SD mismatch repair?
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recognition, excision, resynthesize
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