BIOL 3080H Lecture Notes - Lecture 4: Dna Mismatch Repair, Dna Replication, Dna Ligase
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At the front of the replication fork, dna helicase opens up the dna helix. Two dna polymerases work at the fork; one on the leading strand and one on the lagging strand. Dna polymerase on the leading strand operates in a continuous fashion. Dna polymerase on the lagging strand must restart at short intervals, using an rna primer made by dna primase. A lagging-strand dna polymerase remains bund to the rest of the replication proteins so that it can be reused to synthesize successive okazaki fragments. Additional proteins help to hold the different protein components of the fork together, enabling them to function as a well-coordinated protein machine. An electron micrograph showing the replication machine from the bacteriophage t4 as it moves along a template synthesizing dna behind it. Strand-directed mismatch repair system detects the potential for distortion in the dna helix from the misfit between non-complementary base pairs. Muts and mutl are present in both bacteria and eukaryotic cells.
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4. | A-T base pairs in a DNA double helix | ||||||||||
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12. | What effect would a primase inhibitor have on DNA replication? | ||||||||||
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13. | To replicate their DNA in a timely manner, most eukaryotic chromosomes | ||||||||||
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15. | In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand. | ||||||||||
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QUESTION 1. Choose the true statement about prokaryotic and eukaryotic DNA replication. A.Eukaryotic DNA replication involves less protein factors than does prokaryotic DNA replication. |
B. Prokaryotic DNA polymerases replicate DNA 5' to 3', while eukaryotic DNA polymerases replicate DNA 3' to 5'. |
C. Eukaryotic DNA replication begins at multiple origins of replication, while prokaryotic DNA replication begins at a single origin of replication. |
D. Prokaryotic genomes take longer to replicate than eukaryotic genomes. |
QUESTION 2. Bacterial cells use DNA replication to:
A. make back-up copies of their genome in case of a mutation. |
B. manifest multiple phenotypes at once. |
C. copy their genetic material prior to binary fission. |
D. build functional proteins. |
QUESTION 3. Choose the true statement about the genetic code.
A. A cell's mRNA code is read four nucleotides at a time to specify a single amino acid. |
B. The genetic code encodes 64 amino acids, one for each of the 64 corresponding codons. |
C. The genetic code is redundant, with multiple codons specifying a single amino acid. |
D. The genetic code varies widely among organisms, with each having a different set of codons for a corresponding amino acid. |
QUESTION 4. Of the following enzymes, which are correctly matched with their function? To be marked correct, you'll need to select all correctly matched statements, as there may be more than one correct answer.
A. Helicase, relieves torsion stress as DNA unwinds |
B. Ligase, covalently bonds adjacent Okazaki fragments |
C. Primase, removes RNA primers |
D. DNA polymerase III, builds most of the DNA on the leading and lagging strand |
QUESTION 5. Which of the following contributes to DNA replication accuracy? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.
A. The capacity to proofread improves DNA replication accuracy. |
B. A slow rate of DNA replication contributes to accuracy. |
C. The use of primase improves DNA replication accuracy. |
D. DNA replication accuracy is improved thanks to complementary base pairing rules. |