Initiation DNA replication starts at specific nucleotide sequence called the origin of replication. The enzyme helicase unwinds the DNA by breaking the hydrogen bonds that hold the two polynucleotide strands together. Single-strand binding proteins help stabilize the single strands of DNA and prevent the two strands from re-annealing to each other. As helicase unwinds the DNA, torsional strain occurs on the DNA molecule. The enzyme DNA gyrase relieves this strain. Both single strands of DNA are templates for the creation of the duplicate strand of DNA. DNA replication is said to be semi-conservative because each strand of DNA consists of both an old strand and a newly synthesized strand; therefore, the copied DNA is a template for DNA replication.
Added by Nicholas M.
Step 1
Step 1: The specific nucleotide sequence where initiation of DNA replication starts is called the origin of replication. Show more…
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Some Processes Involved in DNA Replication The replication origin is identified. DNA primase builds RNA primer. Okazaki fragments are spliced by DNA ligase. Helicases bind and uncoil the DNA double helix. RNA primer is the starting point for DNA polymerase. DNA replication ends at the telomere where DNA codes for termination. DNA polymerase adds complementary nucleotides in the 5' to 3' direction in short segments called Okazaki fragments. The sequence in which the events numbered above occur during DNA replication of the lagging strand is:
Anand J.
Place the steps of DNA replication in order. Beginning of DNA replication 1 A different DNA polymerase is recruited and removes the RNA primers and lays down complementary bases to shorten the gaps between Okazaki fragments 2 Ligase is recruited and glues the DNA daughter strand fragments together 3 DNA polymerase lays down complementary nucleotide bases; creating both a continuous daughter strand on the 5'-3' template strand and Okazaki fragments on the 3'-5' template strand 4 Helicase unzips the DNA strands creating replication forks 5 RNA primase is recruited and lays down primers on to the template strand creating both a leading and lagging strand 6 Helicase binds to the origin of replication 7 DNA polymerase is recruited to the 3' end of the newly laid RNA primer Finished Replication
Bryan V.
All DNA polymerases synthesize new DNA strands in the $5^{\prime} \rightarrow 3^{\prime}$ direction. In some respects, replication of the antiparallel strands of duplex DNA would be simpler if there were also a second type of polymerase, one that synthesized DNA in the $3^{\prime} \rightarrow 5^{\prime}$ direction. The two types of polymerase could, in principle, coordinate DNA synthesis without the complicated mechanics required for lagging strand replication. However, no such $3^{\prime} \rightarrow 5^{\prime}$ -synthesizing enzyme has been found. Suggest two possible mechanisms for $3^{\prime} \rightarrow 5^{\prime}$ DNA synthesis. Pyrophosphate should be one product of both proposed reactions. Could one or both mechanisms be supported in a cell? Why or why not? (Hint: You may suggest the use of DNA precursors not actually present in extant cells.)
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