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

Previous problemNext problem

1:12 minutes

Problem 1c

Textbook Question

In the discussion, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions?
How do we know that in vivo DNA synthesis occurs in the 5' to 3' direction?

Verified step by step guidance

Understand the concept of DNA synthesis: DNA synthesis involves the addition of nucleotides to a growing DNA strand during replication. This process is catalyzed by DNA polymerase enzymes.

Review the structure of DNA: DNA strands have directionality, with one end labeled 5' (five prime) and the other 3' (three prime). The 5' end has a phosphate group, while the 3' end has a hydroxyl (-OH) group attached to the sugar molecule.

Examine the role of DNA polymerase: DNA polymerase can only add nucleotides to the 3' hydroxyl group of the growing strand. This restriction means that DNA synthesis proceeds in the 5' to 3' direction, as new nucleotides are added to the 3' end.

Consider experimental evidence: Experiments using radiolabeled nucleotides and DNA synthesis inhibitors have demonstrated that DNA polymerase activity occurs exclusively in the 5' to 3' direction. For example, studies with chain-terminating nucleotides (like dideoxynucleotides) show that synthesis stops when the 3' hydroxyl group is unavailable.

Reflect on the implications for replication: The 5' to 3' directionality of DNA synthesis ensures accurate replication and allows for the leading and lagging strand synthesis during the replication process. This mechanism is essential for maintaining genetic fidelity.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

DNA Replication Directionality

DNA replication occurs in the 5' to 3' direction due to the structure of DNA polymerases, the enzymes responsible for synthesizing new DNA strands. These enzymes can only add nucleotides to the 3' end of a growing DNA strand, which means that the template strand must be read in the 3' to 5' direction. This inherent directionality is crucial for maintaining the fidelity and efficiency of DNA replication.

Role of DNA Polymerase

DNA polymerase is the key enzyme that catalyzes the synthesis of new DNA strands during replication. It requires a primer with a free 3' hydroxyl group to initiate synthesis, which reinforces the 5' to 3' directionality. Different types of DNA polymerases exist, each with specific functions, such as proofreading and repairing DNA, ensuring the integrity of the genetic material.

Experimental Evidence for Directionality

Experimental evidence supporting the 5' to 3' direction of DNA synthesis includes studies using labeled nucleotides and pulse-chase experiments. These methods have shown that newly synthesized DNA strands incorporate nucleotides at their 3' ends, confirming the directionality of synthesis. Additionally, the observation of Okazaki fragments on the lagging strand during replication further illustrates this directional process.

Watch next

Master Directionality with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Multiple Choice

Which of the following proteins is responsible for synthesizing RNA primers?

The short DNA fragments created during lagging strand replication are called what?

In the discussion, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions?

What observations reveal that a 'telomere problem' exists during eukaryotic DNA replication, and how did we learn of the solution to this problem?

466

views

Textbook Question

How do we know that DNA synthesis is discontinuous on one of the two template strands?

435

views

Textbook Question

How was it demonstrated that DNA synthesis occurs under the direction of DNA polymerase III and not polymerase I?

549

views

Textbook Question

Write a short essay that distinguishes between the terms replication and synthesis, as applied to DNA. Which of the two is most closely allied with the field of biochemistry?

478

views

Textbook Question

Compare conservative, semiconservative, and dispersive modes of DNA replication.

1089

views

Textbook Question

Describe the role of ¹⁵N in the Meselson–Stahl experiment.

815

views

Show more practices