/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 4 Draw a molecule of DNA undergoin... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 12: Problem 4

Draw a molecule of DNA undergoing rolling-circle replication. On your drawing, identify (a) origin of replication, (b) polarity (5' and 3' ends) of all template and newly synthesized strands, (c) leading and lagging strands, (d) Okazaki fragments, and (e) locations of primers.

Short Answer

Expert verified
The origin of replication is where the initial nick occurs. The leading strand synthesizes continuously towards the fork, while the lagging strand forms Okazaki fragments that proceed away from the fork, each initiated by primers.

Step by step solution

01

Understand Rolling-Circle Replication

Rolling-circle replication is a process often used by circular DNA molecules, like plasmids. It involves the synthesis of a new DNA strand using one of the original DNA strands as a template. After an initial "nick" at the origin of replication, one end of the DNA strand is displaced as new nucleotides are added.
02

Identify the Origin of Replication

In the drawing, locate the point where the initial "nick" in one DNA strand occurs. Label this as the 'origin of replication.' This is where the replication process begins.
03

Label the Polarity of DNA Strands

For both the template and newly synthesized strands, denote the direction of the strands using the symbols 5' and 3'. The original circular DNA has strands running in opposite directions due to the antiparallel nature of DNA.
04

Identify Leading and Lagging Strands

In the context of rolling-circle replication, identify the leading strand that synthesizes continuously towards the 'open' end. The lagging strand synthesizes DNA fragments going in the opposite direction away from the replication fork.
05

Determine the Okazaki Fragments

On the lagging strand, identify short, periodically synthesized DNA segments. Label these segments as Okazaki fragments, as they are characteristic of lagging strand synthesis.
06

Locate the Primers

Find the starting points for DNA synthesis on the newly synthesized strands. RNA primers must first be laid down for DNA polymerase to begin adding nucleotides. Mark these locations on the drawing.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

DNA replication
DNA replication is the process through which a double-stranded DNA molecule is copied to produce two identical DNA molecules. This is a fundamental process that occurs in all living organisms to ensure that each new cell has the same genetic information. During replication, the DNA helix unwinds, and each strand serves as a template for the synthesis of a new complementary strand. The result is a semi-conservative replication where each new DNA molecule consists of one original strand and one newly synthesized strand.
  • The enzyme helicase unwinds the DNA helix, separating the two strands.
  • DNA polymerase then adds complementary nucleotides to each original strand.
  • This process ensures the genetic information is passed on accurately in cellular division.
Understanding DNA replication is essential, as any errors can lead to mutations, which may cause diseases or malfunctions in an organism.
Leading and lagging strands
In DNA replication, the two strands of the DNA double helix are replicated differently due to their antiparallel orientation. This results in the formation of a leading strand and a lagging strand.
  • **Leading Strand**: This strand is synthesized continuously in the direction of the replication fork movement. Since DNA polymerase can only add nucleotides in the 5' to 3' direction, this is straightforward for the leading strand.
  • **Lagging Strand**: This strand is synthesized discontinuously in short segments, known as Okazaki fragments. The lagging strand runs in the opposite direction to the replication fork, necessitating a more complex replication process.
The coordination and replication of these strands are critical in ensuring the genome is accurately duplicated.
Okazaki fragments
Okazaki fragments are short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication. They are named after the Japanese scientist Reiji Okazaki who discovered them along with his wife Tsuneko.
  • These fragments are necessary because DNA polymerase can only synthesize DNA in the 5' to 3' direction.
  • On the lagging strand, these fragments are later joined together by the enzyme DNA ligase to create a continuous DNA strand.
  • The synthesis of Okazaki fragments involves RNA primers that provide a starting point for DNA polymerase.
Understanding the role and formation of Okazaki fragments is crucial for comprehending how both leading and lagging strands are efficiently replicated.
Origin of replication
The origin of replication is the particular sequence in a genome where DNA replication begins. It is a crucial element in the replication process of both linear and circular DNA. In rolling-circle replication, it is the point where the initial 'nick' in the DNA strand occurs.
  • This site is recognized by initiator proteins which help unwind the DNA at this point.
  • The origin is characterized by a specific sequence of nucleotides, making it a target for replication machinery.
  • In the context of circular DNA, like plasmids, the origin gives rise to continuous synthesis on the leading strand and discontinuous synthesis on the lagging strand.
Recognizing and understanding the origin of replication is vital, as it dictates where and how replication will proceed across the DNA molecule.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

What substrates are used in DNA synthesis?

Phosphorus is required to synthesize the deoxyribonucleoside triphosphates used in DNA replication. A geneticist grows some \(E .\) coli in a medium containing nonradioactive phosphorus for many generations. A sample of the bacteria is then transferred to a medium that contains a radioactive isotope of phosphorus \(\left(^{32} \mathrm{P}\right) .\) Samples of the bacteria are removed immediately after the transfer and after one and two rounds of replication. Assume that newly synthesized DNA contains \(^{32} \mathrm{p}\) and the original DNA contains nonradioactive phosphorus. What will be the distribution of radioactivity in the DNA of the bacteria in each sample? Will radioactivity be detected in neither, one, or both strands of the DNA?

The enzyme telomerase is part protein and part RNA. What would be the most likely effect of a large deletion in the gene that encodes the RNA component of telomerase? How would the function of telomerase be affected?

DNA topoisomerases play important roles in DNA replication and in supercoiling (see Chapter 11 ). These enzymes are also the targets for certain anticancer drugs (see the introduction to this chapter). Eric Nelson and his colleagues studied m-AMSA, one of the anticancer compounds that acts on topoisomerase (E. M. Nelson, K. M. Tewey, and L. F. Liu. \(1984 .\) Proceedings of the National Academy of Sciences of the United States of America 81:1361-1365). They found that m-AMSA stabilizes an intermediate produced in the course of topoisomerase action. The intermediate consists of topoisomerase bound to the broken ends of the DNA. Breaks in DNA that are produced by anticancer compounds such as m-AMSA inhibit the replication of the cellular DNA and thus stop cancer cells from proliferating. Explain how m-AMSA and other anticancer agents that target topoisomerase enzymes taking part in replication might lead to DNA breaks and chromosome rearrangements.

List the different proteins and enzymes taking part in bacterial replication. Give the function of each in the replication process.
See all solutions

Recommended explanations on Biology Textbooks

Microbiology

Read Explanation

Responding to Change

Read Explanation

Energy Transfers

Read Explanation

Bioenergetics

Read Explanation

Chemistry of Life

Read Explanation

Cellular Energetics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.