Term
| What are the 3 possible modes of DNA replication? |
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Definition
conservative
semi-conservative
dispersive |
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Term
| What is conservative DNA replication? |
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Definition
the parental strand is conserved
new strand is synthesized |
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Term
| What is semi-conservative DNA replication? |
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Definition
| each replicated DNA molecule consists of one old and one new strand |
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Term
| What is dispersive DNA replication? |
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Definition
| each strand consists of segments of old and new DNA |
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Term
| Describe the Meselson-Stahl Experiment |
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Definition
-Grow E.coli in 15N solution
-Transfer to 14N solution
-Separate DNA using sedimentation
-determine the amount of 14N vs 15N in each strand of DNA
-can conclude how DNA is replicated
Findings: semi conservative |
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Term
| Who determined the mode of DNA replication? |
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Definition
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Term
| What did Taylor, Woods and Hughs' experiment do? |
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Definition
| Demonstrated semi-conservative DNA with bean root tips |
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Term
| Who used autoradiography to demonstrate the replication of DNA in E.coli and what were their findings? |
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Definition
John Cairns
-found that there is one origin of replication (single locus) called a REPLICON |
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Term
| What is a replicon? What is it called in the E coli chromosome? |
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Definition
a region that replicates DNA from a single origin
oriC |
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Term
| Why are AT-rich regions the site of replication and not GC? |
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Definition
| because A-T bases are held together by only 2 hydrogen bonds, so the strands are easily separated |
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Term
| What was Arthur Kornberg's contribution to research in DNA replication? |
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Definition
-purified an enzyme capable of synthesizing DNA in vitro
-the enzyme adds nucleotides to the 3' end
-DNA strand is synthesized 5'-3' direction |
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Term
| What enzyme catalyzes the addition of nucleotides to replace RNA primers and how does it work? |
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Definition
| DNA polymerase I -acts as nucleophile, displaces H on 3'OH, allows phosphodiester bond to form |
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Term
| What strand is synthesized continuously and which is discontinuous? |
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Definition
leading strand is continuous
lagging is discontinously |
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Term
| How does discontinuous synthesis work? |
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Definition
-lagging strand is synthesized in short Okazaki fragments, each with an
-each fragment has an RNA primer which will be removed by DNA poly 1 & replaced with nucleotides
-ligase joins the ends of the segments |
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Term
| What enzyme separates the two strands of DNA to allow for replication? |
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Definition
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Term
| What enzyme relieves the supercoiling of the DNA? |
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Definition
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Term
| What enzyme joins okazaki fragments? |
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Definition
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Term
| What is necessary for DNA polymerase to begin synthesizing strands? What enzyme does this in the lagging strand? |
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Definition
primers need to be put in place
RNA primase adds them |
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Term
| What prevents separated strands from re-annealing? |
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Definition
| single-stranded binding proteins |
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Term
| What enzyme extends/synthesizes the new strand of DNA |
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Definition
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