Gel Electrophoresis: Principles and Applications in Molecular Biology

Question 1

Which of the following is NOT a technique used in gel electrophoresis?

Accepted Answer

Chromatography

Answer

Agarose gel electrophoresis

Answer

Polyacrylamide gel electrophoresis

Answer

Isoelectric focusing

Question 2

What is the function of the tracking dye in gel electrophoresis?

Accepted Answer

To visualize the movement of the molecules through the gel

Answer

To indicate when the electrophoresis is complete

Answer

To absorb UV light and make the molecules visible

Answer

To increase the conductivity of the gel

Question 3

What is the main difference between native and denaturing gels?

Accepted Answer

Native gels preserve the native structure of the molecules, while denaturing gels do not.

Answer

Denaturing gels preserve the native structure of the molecules, while native gels do not.

Answer

Native gels are used to separate molecules based on size, while denaturing gels are used to separate molecules based on charge.

Answer

Denaturing gels are used to separate molecules based on size, while native gels are used to separate molecules based on charge.

Question 4

Which of the following factors does NOT affect the rate of electrophoresis?

Accepted Answer

Temperature of the electrophoresis buffer

Answer

Applied voltage

Answer

Concentration of the gel

Answer

Size of the molecules

Question 5

What is the purpose of a loading buffer in gel electrophoresis?

Accepted Answer

To facilitate the migration of molecules through the gel

Answer

To add color to the molecules

Answer

To increase the density of the molecules

Answer

To neutralize the charge of the molecules

Question 6

Which type of gel electrophoresis is commonly used to separate proteins?

Accepted Answer

Polyacrylamide gel electrophoresis (PAGE)

Answer

Agarose gel electrophoresis

Answer

Starch gel electrophoresis

Answer

Capillary electrophoresis

Question 7

For DNA fragment separation in the range of 500 bp to 2 kb, what is the optimal agarose gel concentration?

Accepted Answer

1.5%

Answer

1%

Answer

2%

Answer

2.5%

Question 8

Which statement about polyacrylamide gel electrophoresis is incorrect?

Accepted Answer

It is used exclusively for separating small DNA fragments

Answer

It is more expensive than agarose gel electrophoresis

Answer

It is more challenging to prepare than agarose gel electrophoresis

Answer

It is less sensitive than agarose gel electrophoresis

Question 9

In gel electrophoresis, what is the primary role of ethidium bromide?

Accepted Answer

Staining DNA fragments for UV light visualization

Answer

Increasing the density of DNA fragments

Answer

Neutralizing the charge of DNA fragments

Answer

Facilitating DNA fragment migration through the gel

Question 10

Gel electrophoresis relies on which fundamental principle for molecule separation?

Accepted Answer

Size and charge-based separation

Answer

Protein purification from DNA

Answer

RNA sequence analysis

Answer

Nucleic acid quantification

Question 11

In gel electrophoresis, what is the primary role of agarose gel?

Accepted Answer

Providing a separation matrix for molecules

Answer

Conducting electricity for molecule migration

Answer

Allowing UV light visualization of separated molecules

Answer

Enhancing the resolution of small DNA fragments

Question 12

Which of the following techniques is primarily used to determine the concentration of DNA in a sample?

Accepted Answer

Spectrophotometry

Answer

Flow cytometry

Answer

Microscopy

Answer

Gel electrophoresis

Question 13

Which of the following is NOT an application of gel electrophoresis?

Accepted Answer

Cell sorting

Answer

Protein separation

Answer

DNA fingerprinting

Answer

RNA analysis

Question 14

Which of the following factors does NOT affect the migration rate of DNA fragments during gel electrophoresis?

Accepted Answer

Fragment concentration

Answer

DNA size

Answer

Gel concentration

Answer

Electric field strength

Question 15

Which dye is commonly used to visualize DNA fragments in gel electrophoresis?

Accepted Answer

Ethidium bromide

Answer

Coomassie Brilliant Blue

Answer

Alizarin Red

Answer

Sudan Black

Question 16

What is the purpose of running a DNA ladder alongside the samples in gel electrophoresis?

Accepted Answer

To estimate the approximate size of unknown DNA fragments

Answer

To stain the gel evenly

Answer

To calibrate the electric field strength

Question 17

Which type of gel electrophoresis is specifically used for separating proteins?

Accepted Answer

SDS-PAGE

Answer

Native PAGE

Answer

Agarose gel electrophoresis

Answer

Pulsed-field gel electrophoresis

Question 18

How does increasing the gel concentration generally affect the migration of DNA fragments?

Accepted Answer

Slower migration

Answer

No change in migration

Answer

Variable migration depending on fragment size

Answer

Faster migration

Question 19

Which technique can be employed to enhance the separation of DNA fragments on a gel?

Accepted Answer

Gradient gel electrophoresis

Answer

Isoelectric focusing

Answer

Southern blotting

Answer

Capillary electrophoresis

Question 20

What is the primary function of the buffer solution used in gel electrophoresis?

Accepted Answer

To maintain pH and conductivity

Answer

To prevent DNA degradation

Answer

To stain the DNA fragments

Answer

To increase the gel strength

Question 21

What is the typical range of agarose concentrations used in DNA electrophoresis for resolving DNA fragments of moderate size?

Accepted Answer

0.5% to 2.0%

Answer

2.0% to 5.0%

Answer

0.1% to 0.5%

Answer

5.0% to 10.0%

Question 22

Why is ethidium bromide commonly used in gel electrophoresis?

Accepted Answer

Ethidium bromide intercalates with DNA and fluoresces under UV light, allowing visualization of DNA fragments.

Answer

Ethidium bromide enhances the separation of DNA fragments.

Answer

Ethidium bromide increases the conductivity of the gel.

Answer

Ethidium bromide prevents DNA degradation during electrophoresis.

Question 23

Which type of gel is most commonly used for resolving small DNA fragments (<500 bp)?

Accepted Answer

Polyacrylamide gel

Answer

SDS-PAGE gel

Answer

Agarose gel

Answer

Native gel

Question 24

You are analyzing a DNA sample using gel electrophoresis. After running the gel, you observe a single band at the top of the gel. What is the most likely explanation for this result?

Accepted Answer

The DNA fragments are very large and did not migrate significantly through the gel matrix.

Answer

The DNA was not loaded correctly into the wells.

Answer

The gel was not run long enough for the fragments to separate properly.

Answer

The DNA fragments are very small and migrated rapidly through the gel.

Question 25

Which of the following is a common application of gel electrophoresis in molecular biology research?

Accepted Answer

DNA fingerprinting for forensic analysis and paternity testing.

Answer

Protein synthesis, the process of creating proteins from genetic information.

Answer

Transcription, the process of copying DNA into RNA.

Answer

Cellular respiration, the process of energy production in cells.

Question 26

How does the concentration of agarose in a gel affect the separation of DNA fragments during electrophoresis?

Accepted Answer

Higher agarose concentration creates smaller pores in the gel matrix, resulting in better separation of smaller DNA fragments.

Answer

Higher agarose concentration creates larger pores in the gel matrix, resulting in better separation of larger DNA fragments.

Answer

Agarose concentration has no significant effect on the separation of DNA fragments.

Question 27

What is the role of the electric field in gel electrophoresis?

Accepted Answer

The electric field provides the driving force for the movement of charged DNA fragments through the gel matrix.

Answer

The electric field prevents DNA degradation during electrophoresis.

Answer

The electric field enhances the binding of ethidium bromide to DNA.

Question 28

You are performing gel electrophoresis to analyze a PCR product. You observe two bands on the gel, one at 500 bp and another at 1000 bp. What does this suggest about the PCR reaction?

Accepted Answer

The PCR reaction yielded two different DNA fragments, likely due to the presence of multiple target sequences or primer dimer formation.

Answer

The PCR reaction was unsuccessful, as multiple bands indicate non-specific amplification.

Answer

The DNA sample was contaminated, leading to the amplification of extraneous DNA fragments.

Question 29

Which of the following is NOT a common method for visualizing DNA fragments in gel electrophoresis?

Accepted Answer

Fluorescent microscopy

Answer

Silver staining

Answer

Ethidium bromide staining

Answer

SYBR Green staining