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The document provides an overview of DNA electrophoresis, a technique for separating DNA fragments by size using an electric field. It includes prelab questions addressing the use of agarose gel, safety precautions, and the importance of buffer solutions, as well as post lab questions on interpreting results and troubleshooting issues. The significance of controls and the impact of PCR amplification on results are also discussed.

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42 views2 pages

Telegram 1

The document provides an overview of DNA electrophoresis, a technique for separating DNA fragments by size using an electric field. It includes prelab questions addressing the use of agarose gel, safety precautions, and the importance of buffer solutions, as well as post lab questions on interpreting results and troubleshooting issues. The significance of controls and the impact of PCR amplification on results are also discussed.

Uploaded by

davidanani94
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Prelab and Post Lab Questions on Practical DNA Electrophoresis

1. Understanding DNA Electrophoresis

DNA electrophoresis is a laboratory technique used to separate DNA fragments based on their
size. This process involves applying an electric field to a gel matrix, causing the negatively
charged DNA molecules to migrate towards the positive electrode. The smaller fragments move
faster through the gel than larger ones, allowing for separation.

2. Prelab Questions

What is the purpose of using agarose gel in DNA electrophoresis?


Agarose gel provides a porous medium that allows for the separation of DNA fragments by size.
The concentration of agarose can be adjusted to optimize resolution for different sizes of DNA.

What safety precautions should be taken when handling ethidium bromide or other
intercalating agents?
Ethidium bromide is a mutagen and should be handled with gloves and protective eyewear. It
should be disposed of according to hazardous waste protocols.

How do you prepare a standard DNA ladder, and why is it important?


A standard DNA ladder consists of known concentrations of DNA fragments that serve as a
reference for estimating the size of unknown samples during electrophoresis.

What role does buffer solution play in the electrophoresis process?


The buffer maintains pH and ionic strength, ensuring consistent migration of DNA through the
gel while also providing ions that facilitate electrical conductivity.

What are some common sources of error in preparing samples for electrophoresis?
Errors may include improper dilution of samples, contamination, or incorrect loading techniques
which can affect results.
3. Post Lab Questions

How do you interpret the results obtained from a gel electrophoresis experiment?
Results are interpreted by comparing band positions against the DNA ladder; distances traveled
correlate with fragment sizes.

What factors could affect the migration speed of DNA during electrophoresis?
Factors include agarose concentration, voltage applied, buffer composition, and temperature
during the run.

How would you troubleshoot if no bands are visible after staining?


Possible troubleshooting steps include checking sample preparation methods, ensuring proper
loading techniques, verifying that the gel was not overloaded, or confirming that staining
procedures were correctly followed.

Discuss how PCR amplification affects results in electrophoresis.


PCR amplification increases the quantity of specific DNA sequences which can lead to clearer
bands on an electrophoresis gel but may also introduce artifacts if not optimized properly.

Why is it important to include controls in your experiment?


Controls help validate results by providing benchmarks against which experimental data can be
compared; they ensure that any observed effects are due to experimental conditions rather than
external variables.

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