Unraveling DNA: A Gel Electrophoresis Journey

Biology Grades High School 5:00 Video
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Lesson Description

Explore the principles and applications of gel electrophoresis, a fundamental technique for separating DNA fragments based on size and charge.

Video Resource

Gel electrophoresis

khanacademymedicine

Duration: 5:00
Watch on YouTube

Key Concepts

  • DNA's negative charge
  • Size-based separation of molecules
  • The role of an electric field
  • DNA ladder as a reference standard

Learning Objectives

  • Describe the principle of gel electrophoresis.
  • Explain how DNA fragments are separated by size using an electric field.
  • Explain the purpose of a DNA ladder and how it's used to determine fragment size.
  • Describe the basic components of the electrophoresis setup (gel, wells, electrodes, buffer).

Educator Instructions

  • Introduction (5 mins)
    Begin by engaging students with a question: 'Imagine you have a mixture of DNA fragments of different sizes. How could you separate them?' Briefly introduce gel electrophoresis as a technique used for this purpose. Show the Khan Academy video as the central learning resource.
  • Video Viewing (7 mins)
    Play the Khan Academy video 'Gel electrophoresis'. Instruct students to take notes on the key principles, materials, and applications of the technique.
  • Discussion (10 mins)
    Facilitate a class discussion to reinforce understanding. Use the discussion questions provided.
  • Interactive Exercise: Gel Electrophoresis Simulation (15 mins)
    Students use a virtual gel electrophoresis simulation (link provided in interactive exercises) to manipulate variables such as DNA fragment size and voltage to observe the effects on DNA migration.
  • Wrap-up and Quiz (8 mins)
    Summarize the key concepts learned in the lesson. Administer the multiple-choice and fill-in-the-blank quizzes to assess understanding.

Interactive Exercises

  • Gel Electrophoresis Simulation
    Students will use a virtual gel electrophoresis simulation to separate DNA fragments of known base pair length and determine the identity of unknown samples. (e.g., use a simulator from LabXchange or similar platform)

Discussion Questions

  • Why does DNA migrate towards the positive electrode in gel electrophoresis?
  • How does the size of a DNA fragment affect its migration speed?
  • What is the purpose of the DNA ladder in gel electrophoresis?
  • Can you think of any real-world applications of gel electrophoresis?

Skills Developed

  • Critical thinking
  • Data interpretation
  • Scientific reasoning
  • Application of concepts

Multiple Choice Questions

Question 1:

What property of DNA allows it to be separated by gel electrophoresis?

Correct Answer: Negative charge

Question 2:

In gel electrophoresis, smaller DNA fragments migrate:

Correct Answer: Faster than larger fragments

Question 3:

What is the purpose of the DNA ladder in gel electrophoresis?

Correct Answer: To provide a size standard for DNA fragments

Question 4:

The gel used in gel electrophoresis is typically made of:

Correct Answer: Agarose or polyacrylamide

Question 5:

What provides the driving force for DNA migration in gel electrophoresis?

Correct Answer: Electrical current

Question 6:

Where are the DNA samples loaded onto the gel for electrophoresis?

Correct Answer: Wells at the top of the gel

Question 7:

If a DNA fragment migrates a shorter distance than another fragment, it is likely:

Correct Answer: Larger

Question 8:

Which of the following is NOT a step in gel electrophoresis?

Correct Answer: Denaturing the DNA with heat

Question 9:

What charge is applied at the bottom of the gel?

Correct Answer: Positive charge

Question 10:

What do the DNA bands on the gel represent?

Correct Answer: Different DNA Fragments

Fill in the Blank Questions

Question 1:

Gel electrophoresis separates DNA fragments based on their ________.

Correct Answer: size

Question 2:

DNA has a ________ charge, which causes it to move toward the positive electrode.

Correct Answer: negative

Question 3:

A ________ is used as a size standard to estimate the size of unknown DNA fragments.

Correct Answer: DNA ladder

Question 4:

The gel used in gel electrophoresis is typically made of agarose or ________.

Correct Answer: polyacrylamide

Question 5:

The DNA samples are loaded into ________ at the top of the gel.

Correct Answer: wells

Question 6:

During electrophoresis, the smallest DNA fragments migrate the ________.

Correct Answer: furthest

Question 7:

An ________ ________ is applied to the gel to separate the DNA fragments.

Correct Answer: electrical current

Question 8:

The bands that appear on the gel after electrophoresis represent different ________ ________.

Correct Answer: DNA fragments

Question 9:

What charge is applied at the top of the gel?

Correct Answer: negative

Question 10:

Gel electrophoresis is valuable tool for analyzing and ______ DNA.

Correct Answer: separating

Educational Standards

B.LS1.1:Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. B.LS3.1:Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. B.LS4.1:Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence.

Teaching Materials

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