Replication Unit for NW 04-350
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| conservative model | hypothetical explanation of how replication might occur. supposes that the original double stranded molecule will remain fully intact after replication is complete and the new double stranded molecule will be entirely composed of new material
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| dispersive model | hypothetical explanation of how replication might occur. supposes that the original strands of nucleic acid will be broken into chunks and distributed (dispersed) in both double stranded molecules after replication is complete
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| semiconservative model | hypothetical explanation of how replication might occur. supposes that each strand of the original double stranded molecule remain intact but after replication one strand is paired with one entirely new strand. this hypothesis is supported by data.
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| density gradient centrifugation | technique used to separate molecules with different densities (mass) by passing through a solution of layered densities
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| light nitrogen | an isotope of nitrogen (N14) with one fewer neutron than heavy nitrogen
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| heavy nitrogen | an isotope of nitrogen (N15) with an extra neutron and therefore more mass than light nitrogen
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| origin | site on the chromosome where replication will begin, binding site for initiator protein
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| replication fork | Y shaped structure where the two strands of DNA have separated to serve as templates for replication. each origin will generate two replication forks
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| DNA polymerase | enzyme that uses dNTP as a substrate to generate a new strand of DNA in a 5' to 3' direction
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| DNA polymerase III | the prokaryotic form of DNA polymerase that is responsible for synthesizing the majority of the DNA during replication. has higher affinity than other polymerases.
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| DNA polymerase I | the more abundant form of DNA polymerase in prokaryotes. has less affinity but can synthesize DNA. can also act as exonuclease in 5' to 3' direction which allows it to remove RNA primers
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| de novo synthesis | the ability of a polymerase to bind to a nucleic acid template and begin synthesizing a complementary strand without anything in place prior to that synthesis. RNA polymerase can do this. DNA polymerases can't
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| single stranded binding proteins (SSB) | proteins that bind to single stranded DNA formed in the replication fork. used to keep the two strands separated from each other.
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| helicase | enzyme used to separate the strands of DNA at the replication fork during replication. one helicase per replication fork
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| gyrase | enzyme that moves in front of the helicase, reducing torsional strain on the DNA molecule created when unwinding occurs
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| primase | enzyme that synthesizes a small segment of RNA to serve as a primer for initiation of replication.
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| RNA primer | needed to provide a 3' OH that DNA polymerases can attach dNTP to when initiating replication. needed because of DNA polymerases inability to carry out de novo synthesis
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| leading strand | strand of new DNA being synthesized in the same direction that the helicase is moving. uninterrupted continuous synthesis until the end is reached
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| lagging strand | strand of new DNA being synthesized in the opposite direction that the helicase is moving. goes through periodic starts and stops as new template is exposed behind it
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| Okazaki fragments | interrupted segments of replicated DNA, especially on the lagging strand. extends from the 5' end of the primer to the 3' nick
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| nick | missing phosphodiester bond between the 3' end of one okazaki fragment and the 5' end of the next okazaki fragment in the chain
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| 5' to 3' exonuclease | the ability of DNA polymerase I to remove nucleotides moving in a 5' to 3' direction. this ability allows this enzyme to remove the RNA primer and replace it with DNA
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| 3' to 5' exonuclease | the ability of both DNA polymerase I and III to remove nucleotides in a 3' to 5' direction (backwards). the backspace function that helps to prevent mutations
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Created by:
jthorns
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