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18 Cards in this Set
- Front
- Back
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What is the C value paradox? |
The complexity of the organism is not proportional to the number of genes in that organism. Only the minimum amount of DNA increases with rising complexity. |
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On which end of the DNA strand are new nucleotides added? |
3' |
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What enzyme joins the primer to the template strand? |
Primase |
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What is the name of the DNA region where the helicase, polymerase, and primase meet? |
Replication fork |
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Why does the polymerase encounter problems when forming the lagging strand? |
Because it is replicated in the 5' to 3' direction, replication must somehow occur in the opposite direction to the replication fork. |
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How does the polymerase forming the lagging strand overcome its problems? |
A new primer is formed every few hundred bases and they are then elongated in fragments called Okazaki fragments. The fragments are joined via DNA ligase. |
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True or false: DNA replication is uni-directional |
False, it is bi-directional. The replication proceeds in both directions from the point of origin. |
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What stops the polymerase enzyme slipping off the DNA strand? |
Sliding clamp subunits |
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What is the site of initiation of replication in E. coli? |
The 245 bp oriC locus |
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Why are TATA sequences easier to unwind than CGCG sequences? |
Thymine and Adenine form two hydrogen bonds, whereas cytosine and guanine form three |
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What protein directs initiation of the replication process in E. Coli? |
DNAa |
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What does DNAa do? |
Binds to sites on the DNA strand. The DNAa subunits join together forming a DNAa hexamer, allowing other proteins to bind such as helicase, DNAb, DNAc |
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What protein facilitates DNAb loading? |
DNAc |
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What is the main replicative polymerase in E. Coli? |
Polymerase III |
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What is the role of polymerase I in E. Coli? |
Polymerase I has 5' to 3' exonuclease activity so erases the RNA primer and fills in the gaps in the lagging strand |
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How many copies of the core DNA polymerase are there in polymerase III and what does this allow? |
Two - this allows simultaneous replication of the leading and lagging strand |
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What is the role of DNAb? |
Unwinds the double stranded DNA ahead of the complex (helicase). |
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What is the role of type I and type II topoisomerases? |
Relaxing and inducing supercoils respectively |
