Term
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Definition
| DnaA protein binds to specific nucleotide sequences at the origin of replication, causing short, tandemly arranged (one after the other) AT-rich regions in the origin to melt. Melting is ATP-dependent, and results in strand separation with the formation of localized regions of ssDNA. |
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Term
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Definition
| These enzymes bind to ssDNA near the replication fork, and then move into the neighboring double-stranded region, forcing the strands apart—in effect, unwinding the double helix. Helicases require energy provided by ATP |
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Term
| Type I DNA topoisomerases |
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Definition
| These enzymes reversibly cut one strand of the double helix. They have both nuclease (strand-cutting) and ligase (strand-resealing) activities. They do not require ATP, but rather appear to store the energy from the phosphodiester bond they cleave, reusing the energy to reseal the strand |
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Term
| Type II DNA topoisomerases |
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Definition
| These enzymes bind tightly to the DNA double helix and make transient breaks in both strands. The enzyme then causes a second stretch of the DNA double helix to pass through the break and, finally, reseals the break (Figure 29.13). As a result, both negative and positive supercoils can be relieved by this ATP-requiring process. |
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Term
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Definition
| synthesizes the short stretches of RNA (approximately 10 nucleotides long) that are complementary and antiparallel to the DNA template. |
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Term
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Definition
| makes the RNA primer required for leading strand synthesis, and initiates Okazaki fragment formation in lagging strand synthesis |
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Term
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Definition
| 3--5' exonuclease activity; begins to add nucleotides along the single-stranded template that specifies the sequence of bases in the newly synthesized chain; can only remove one nucleotide at a time |
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Term
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Definition
| 5-->3' exonuclease and removes the primer (can move a single or groups of nucleotides |
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Term
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Definition
| has a proofreading ability; continues to synthesize DNA on the lagging strand until it is blocked by proximity to an RNA primer |
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Term
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Definition
| initiates the DNA synthesis in the leading strand and in the begining of the ozaki fragments on the lagging strand |
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Term
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Definition
| recruited to complete DNA synthesis on the leading strand and elongate each Okazaki fragment, using 3′→5′ exonuclease activity to proofread the newly synthesized DNA. |
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Term
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Definition
| replicates mitochondrial DNA. |
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Term
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Definition
| contains a protein that acts as a reverse transcriptase, and a short piece of RNA that acts as a template |
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Term
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Definition
| are RNA-directed DNA polymerases and involved in the replication of retroviruses |
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