GeneticsLesson 1 of 2 in the course Mechanisms of Microbial Genetics

DNA Replication: Models, Mechanisms, and Chromosome Ends

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

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Summary

DNA replication makes an accurate copy of genetic information before a cell divides. This lesson introduces the three proposed models of DNA copying and explains how an isotope-labeling experiment established which model is correct.

The double helix consists of two complementary strands. During replication, the strands separate and each can provide the sequence information for building a complementary strand. Scientists initially proposed three ways that the old and new DNA could be arranged.

All flashcards

What is semiconservative DNA replication?
Each daughter DNA molecule contains one parental strand and one newly synthesized complementary strand.
What did the dispersive model propose?
Old and newly synthesized DNA segments are interspersed within the strands of each daughter molecule.
What did the two bands after two generations in the Meselson–Stahl experiment indicate?
Intermediate-density hybrid DNA and light DNA, supporting semiconservative replication.
What does a sliding clamp do during DNA replication?
It helps keep DNA polymerase attached to DNA during synthesis.
How does telomerase help maintain chromosome ends?
It uses its RNA template to extend the 3′ end of chromosome DNA.

Quiz questions

  1. Where does chromosomal DNA replication begin in E. coli?Answer: At the origin called oriC.
  2. In which direction does DNA polymerase extend a newly synthesized DNA strand?Answer: From 5′ to 3′.
  3. Why does the lagging strand form Okazaki fragments?Answer: Its template orientation requires discontinuous synthesis while polymerase extends DNA 5′ to 3′.
  4. How does telomerase extend the end of a linear chromosome?Answer: It uses an internal RNA template to add DNA to the chromosome’s 3′ end.
  5. What happens first in the rolling-circle replication mechanism described for circular DNA?Answer: An enzyme nicks one strand at the double-stranded origin, creating a free 3′-OH.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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