Molecular biologyLesson 1 of 3 in the course Molecular Biology

DNA Replication, Telomeres, and DNA Repair

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

DNA replication makes a copy of a cell’s DNA before it divides, helping ensure that each daughter cell receives the same genetic information. This lesson introduces the copying principle and explains how eukaryotic cells replicate DNA, including how they address the ends of linear chromosomes.

DNA consists of two strands whose bases pair according to a consistent rule: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). Because the strands are complementary, the sequence of one strand determines the sequence of the other. For example, the complement of AGTCATGA is TCAGTACT.

All flashcards

What is semiconservative DNA replication?
Replication that produces DNA molecules, each with one parental strand and one newly synthesized strand.
What are origins of replication?
Specific DNA sequences where replication begins; eukaryotic chromosomes typically have multiple origins.
How are the leading and lagging strands synthesized?
The leading strand is synthesized continuously toward the fork; the lagging strand is made as Okazaki fragments.
What is nucleotide excision repair?
A repair pathway that removes a damaged DNA section and replaces it using the undamaged strand as a template.
How does telomerase extend chromosome ends?
It uses an RNA template to add repetitive DNA sequences to chromosome ends.

Quiz questions

  1. What does semiconservative replication produce?Answer: Two DNA molecules, each with one parental strand and one new strand.
  2. Which enzyme unwinds and opens DNA at a replication origin?Answer: Helicase
  3. Why is the lagging strand synthesized in short sections?Answer: DNA polymerase works 5′ to 3′, so this strand is synthesized discontinuously.
  4. What does mismatch repair do when an incorrectly paired base remains after replication?Answer: It recognizes the mismatch, removes the affected base, and replaces it.
  5. Which repair pathway helps correct thymine dimers caused by ultraviolet exposure?Answer: Nucleotide excision repair

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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