DNA Replication quiz #1 Flashcards
DNA Replication quiz #1
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What does it mean that DNA replication is semi-conservative, and how does this process ensure genetic continuity?
DNA replication is semi-conservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This ensures genetic continuity by preserving half of the original DNA in each daughter molecule, reducing the chance of errors being passed on. Describe the roles of DNA polymerase, primase, helicase, and ligase during DNA replication.
DNA polymerase synthesizes new DNA strands in the 5' to 3' direction; primase creates short RNA primers to provide a starting point for DNA polymerase; helicase unwinds the DNA double helix; and ligase joins Okazaki fragments on the lagging strand to form a continuous DNA strand. Why are telomeres and the enzyme telomerase important for the replication of linear chromosomes in eukaryotic cells?
Telomeres are repetitive, non-coding DNA sequences at chromosome ends that protect coding regions from degradation. Telomerase extends telomeres, allowing complete replication of the lagging strand and preventing loss of essential genetic information during cell division. How does DNA polymerase proofread newly synthesized DNA, and what is the significance of its 3' to 5' exonuclease activity?
DNA polymerase proofreads by checking each newly added nucleotide; if a mismatch is detected, its 3' to 5' exonuclease activity removes the incorrect base, allowing the correct one to be inserted. This proofreading greatly increases the fidelity of DNA replication. What does it mean that DNA replication is semi-conservative, and how does this process ensure genetic continuity?
DNA replication is semi-conservative, meaning each new DNA molecule contains one original (parental) strand and one newly synthesized strand. This preserves half of the original DNA in each daughter molecule, reducing the chance of errors being passed on. Describe the roles of DNA polymerase, primase, helicase, and ligase during DNA replication.
DNA polymerase synthesizes new DNA strands in the 5' to 3' direction; primase creates short RNA primers to provide a starting point for DNA polymerase; helicase unwinds the DNA double helix; and ligase joins Okazaki fragments on the lagging strand to form a continuous DNA strand. Why are telomeres and the enzyme telomerase important for the replication of linear chromosomes in eukaryotic cells?
Telomeres are repetitive, non-coding DNA sequences at chromosome ends that protect coding regions from degradation. Telomerase extends telomeres, allowing complete replication of the lagging strand and preventing loss of essential genetic information during cell division. How does DNA polymerase proofread newly synthesized DNA, and what is the significance of its 3' to 5' exonuclease activity?
DNA polymerase proofreads by checking each newly added nucleotide; if a mismatch is detected, its 3' to 5' exonuclease activity removes the incorrect base, allowing the correct one to be inserted. This proofreading greatly increases the fidelity of DNA replication. What is the difference between the synthesis of the leading and lagging strands during DNA replication?
The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously as Okazaki fragments, which are later joined together by DNA ligase. Why can new nucleotides only be added to the 3' end of a growing DNA strand during replication?
New nucleotides can only be added to the 3' end because the 3' hydroxyl group attacks the phosphate group of the incoming dNTP, releasing energy needed for bond formation. The 5' end cannot participate in this reaction, so elongation only occurs at the 3' end.
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