Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

8. DNA Replication

Overview of DNA Replication

Genetics

8. DNA Replication

Overview of DNA Replication

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2:26 minutes

Problem 15

Textbook Question

Diagram a replication fork in bacterial DNA and label the following structures or molecules.
a. DNA pol III
b. Helicase
c. RNA primer
d. Origin of replication
e. leading strand (label its polarity)
f. DNA pol I
g. Topoisomerase
h. SSB protein
i. Lagging strand (label its polarity)
j. Primase
k. Okazaki fragment

Verified step by step guidance

Start by drawing a replication fork, which is a Y-shaped structure formed during DNA replication. This fork represents the point where the double-stranded DNA is being unwound into two single strands.

Label the origin of replication (d). This is the specific sequence in the DNA where replication begins. It is located at the base of the replication fork.

Indicate the direction of the leading strand (e) and lagging strand (i). The leading strand is synthesized continuously in the 5' to 3' direction, moving toward the replication fork. The lagging strand is synthesized discontinuously in the 5' to 3' direction, moving away from the replication fork, and consists of Okazaki fragments (k).

Add the enzymes and proteins involved in replication: (b) helicase unwinds the DNA at the replication fork, (h) SSB proteins stabilize the unwound single strands, (g) topoisomerase relieves supercoiling ahead of the fork, and (j) primase synthesizes RNA primers (c) to initiate DNA synthesis.

Label the DNA polymerases: (a) DNA pol III synthesizes the new DNA strand by adding nucleotides to the RNA primer, and (f) DNA pol I replaces the RNA primers with DNA nucleotides on the lagging strand.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Replication

DNA replication is the biological process by which a cell duplicates its DNA, ensuring that each daughter cell receives an identical copy. This process involves unwinding the double helix structure of DNA, synthesizing new strands using existing strands as templates, and requires various enzymes and proteins to facilitate the accurate and efficient copying of genetic material.

Enzymes Involved in DNA Replication

Several key enzymes play critical roles in DNA replication. DNA polymerase III synthesizes new DNA strands, helicase unwinds the DNA double helix, primase synthesizes RNA primers to initiate replication, and DNA polymerase I replaces RNA primers with DNA. Topoisomerase alleviates the tension created ahead of the replication fork, while single-strand binding (SSB) proteins stabilize unwound DNA strands.

Leading and Lagging Strands

During DNA replication, the leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, which are later joined together. The leading strand has a 5' to 3' polarity, whereas the lagging strand is synthesized in the opposite direction, requiring multiple RNA primers for initiation.

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Related Practice

Textbook Question

Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.

If a strain of E. coli acquired a mutation that inactivated DNA polymerase III function, would the cell be able to replicate its DNA? Why or why not?

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Textbook Question

Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.

Identify the principal functions of each molecule.

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Textbook Question

Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.

If mutation inactivated DNA polymerase I in a strain of E. coli, would the cell be able to replicate its DNA? If so, what kind of abnormalities would you expect to find in the cell?

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Textbook Question

Distinguish between

(a) unidirectional and bidirectional synthesis, and

(b) continuous and discontinuous synthesis of DNA.

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Textbook Question

List the proteins that unwind DNA during in vivo DNA synthesis. How do they function?

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