DNA Replication Flashcards
What is the leading strand in DNA replication, and how is it synthesized?
The leading strand is the DNA strand synthesized continuously during replication. DNA polymerase synthesizes it in the 5’ to 3’ direction, following the replication fork as it opens.
Describe the role of the primase in DNA replication.
Primase is an enzyme that synthesizes short RNA primers on the lagging strand template. These primers provide a starting point for DNA polymerase to begin replication.
Explain the process of DNA synthesis on the lagging strand.
DNA synthesis on the lagging strand occurs in short fragments called Okazaki fragments. DNA polymerase synthesizes each Okazaki fragment from 5’ to 3’ away from the replication fork, and then they are joined by DNA ligase.
Detail the steps of DNA replication, including the enzymes involved.
DNA replication involves initiation, elongation, and termination. Key enzymes include DNA helicase, DNA polymerase, primase, and DNA ligase.
Explain the process of DNA replication.
DNA replication is the process by which a cell makes an identical copy of its DNA. It involves unwinding the DNA double helix, using complementary base pairing to synthesize new strands, and forming two identical DNA molecules.
When does DNA replication occur in the cell cycle?
DNA replication occurs during the S stage (synthesis stage) of the cell cycle.
Explain the semi-conservative nature of DNA replication.
DNA replication is semi-conservative because one strand of the final DNA molecule is the original DNA, and the other strand is newly synthesized.
What does it mean that DNA strands are anti-parallel?
DNA strands are anti-parallel, meaning they run in opposite directions. One strand goes from 3’ to 5’, while the other runs from 5’ to 3’. This arrangement is due to the numbering of carbons in the sugar of the DNA molecule.
What role does the enzyme helicase play in DNA replication?
Helicase is responsible for unzipping the DNA molecule by breaking the comparatively weak hydrogen bonds between the complementary base pairs.
Where do the nucleotides used to produce the new strands of DNA come from?
Nucleotides used to produce the new DNA strands are sourced from within the nucleus of the cell.
How does DNA polymerase III contribute to DNA replication?
DNA polymerase III adds new nucleotides to the 3’ end of the original DNA strand during replication. It ensures that adenine (A) bonds with thymine (T) and cytosine (C) bonds with guanine (G), producing a continuous strand.
Why can DNA polymerase only add nucleotides to the 3’ end of the original strand during replication?
DNA polymerase is only able to add nucleotides to the 3’ end of the original strand due to its structure and function. As a result, it must work from the replication fork down the strand, producing small fragments known as Okazaki fragments.
Why is an RNA primer produced during DNA replication?
An RNA primer is produced to provide a starting point for DNA polymerase to attach to the single-stranded DNA template and initiate copying.
How does DNA polymerase III add nucleotides during replication, and what happens when it reaches a primer?
DNA polymerase III adds nucleotides using the complementary base pairing rule. When it reaches a primer, it is released. The segment of DNA synthesized in this manner is known as an Okazaki fragment.
What is the role of DNA polymerase I in DNA replication?
DNA polymerase I removes the RNA primer and fills the gap with DNA nucleotides, preparing the DNA strand for further processing.
