MD105 - Forensic DNA Fingerprinting Lab Exercise

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Questions and Answers

What happens to DNA fragments during agarose gel electrophoresis?

They are cut into smaller fragments.

They migrate towards the negative electrode.

They are separated based on their size. (correct)

They remain stationary within the wells.

Which statement accurately describes the role of restriction enzymes?

They alter the charge of DNA fragments.

They stain the DNA for visualization.

They amplify DNA sequences for analysis.

They cut DNA at specific sequences. (correct)

What is the driving force for the movement of DNA fragments in gel electrophoresis?

The density of the gel matrix.

The temperature of the gel.

The applied electric current. (correct)

The size of the wells.

Which of the following best explains why DNA fragments are stained after electrophoresis?

To enable visualization under UV light. Signup and view all the answers

What is the primary purpose of loading a DNA ladder in agarose gel electrophoresis?

To compare fragment sizes. Signup and view all the answers

What is the primary function of the agarose gel in electrophoresis?

To separate nucleic acids based on their size Signup and view all the answers

Which statement best describes the migration of nucleic acids during agarose gel electrophoresis?

Nucleic acids migrate from cathode to anode Signup and view all the answers

What is the purpose of the loading dye in the electrophoresis procedure?

To monitor the progress of electrophoresis Signup and view all the answers

During the restriction digest procedure, what is the expected temperature and duration for incubation of the samples?

45 min at 37°C Signup and view all the answers

Which of the following components is NOT involved in the preparation of a 1% agarose gel?

Sodium Chloride Signup and view all the answers

What is the role of GelRed in the electrophoresis setup?

To visualize the DNA fragments after electrophoresis Signup and view all the answers

What should be avoided to prevent the agarose gel solution from boiling over during preparation?

Heating at a constant high temperature Signup and view all the answers

How should the agarose gel be solidified after pouring into the casting tray?

Left at room temperature until hardened Signup and view all the answers

What is the main purpose of DNA fingerprinting in criminal investigations?

To establish a link between biological evidence and a suspect Signup and view all the answers

Which of the following best describes Restriction Fragment Length Polymorphism (RFLP)?

A type of polymorphism due to variation in DNA sequences recognized by enzymes Signup and view all the answers

What role does agarose gel electrophoresis play in DNA fingerprinting?

It separates DNA fragments based on size Signup and view all the answers

What type of sample was collected from the victim to identify the murderer?

Skin cells found under the victim's fingernails Signup and view all the answers

What is the significance of using multiple suspects' DNA samples in the investigation?

To compare the DNA patterns for identification of the murderer Signup and view all the answers

What is the first step in performing restriction digest for the RFLP technique?

Isolate DNA from the suspects Signup and view all the answers

What determines the pattern of DNA fragment sizes in RFLP analysis?

The type of restriction enzymes used and the individual's DNA sequence Signup and view all the answers

Which suspect could be ruled out as having DNA under the victim's fingernails if his DNA is not found in the analysis?

EUC campus security Signup and view all the answers

Study Notes

MD105 - Cellular Biology Laboratory - Lab Exercise 3: Forensic DNA Fingerprinting

Forensic DNA Fingerprinting: A laboratory technique used to link biological evidence to a suspect in a criminal investigation.
Theoretical Background:
- Introduction to DNA Fingerprinting: This explains the basics of DNA, its structure, and how variations in DNA sequences can be used to identify individuals.
- Restriction Digest of DNA Samples: This explains the process of cutting DNA at specific sequences using restriction enzymes.
- Agarose Gel Electrophoresis Principle: This principle explains how DNA fragments are separated based on their size.
Methodology and Protocol:
- Sample and Agarose Gel Preparation: This describes the steps involved in preparing the agarose gel for electrophoresis.
- Electrophoresis of DNA Samples: This outlines the steps of running the electrophoresis.
- Analysis and Interpretation of Results: This process details how results are evaluated to identify matches
The Crime:
- An EUC Medical student was found brutally stabbed at the university parking lot.
- The CSI Nicosia Department requested help from fellow medical students to find the murderer.
- The students agreed to assist in the investigation.
The Clues:
- Evidence suggests a violent struggle at the scene.
- DNA was collected from skin cells under the victim's fingernails.
The Suspects:
- Five suspects were identified: The heartbroken ex-girlfriend, the jealous brother, the girlfriend, EUC campus security, and the father of the heartbroken ex-girlfriend.
The Plan:
- The students worked together to solve the mystery.
- Experimental procedures were used to isolate suspect DNA and compare it to the victim’s DNA using the RFLP technique.
- DNA fingerprinting is a laboratory technique used to establish a link between biological evidence and a suspect in a criminal investigation.
Restriction Fragment Length Polymorphism (RFLP):
- A type of polymorphism that results from variations in the DNA sequence recognized by restriction enzymes.
- A short genomic site of four to eight nucleotides long is polymorphic when it differs among individuals.
- The DNA is treated with restriction enzymes that cut the DNA into fragments of various lengths.
- The resulting fragments are separated according to their lengths, and the pattern of fragment sizes will differ for each individual tested.
Experimental Procedure (Part A: Restriction Digest):
- DNA samples are added to microcentrifuge tubes.
- Enzyme mix (ENZ) is also transferred to the tubes, followed by mixing the contents of the tubes.
- The tubes are incubated for 45 minutes at a specific temperature (37°C in waterbath).
- DNA samples should contain the following:
  - Crime Scene DNA
  - Suspect 1 DNA
  - Suspect 2 DNA
  - Suspect 3 DNA
  - Suspect 4 DNA
  - Suspect 5 DNA
Experimental Procedure (Part B: Agarose Gel Electrophoresis and Visualization of DNA Fragments):
- A 1% agarose gel is prepared
- The agarose gel is placed an electrophoresis chamber & covered in TAE buffer.
- DNA samples containing loading dye are placed in wells.
- Electrophoresis is run for a specified time.
- The gels are visualized using a UV transilluminator to compare DNA patterns.
RFLP markers inheritance & test validity (a diagram) provides information about genotype inheritance among family members using RFLP markers.
Agarose Gel Electrophoresis Principle: Explains how agarose gel electrophoresis separates nucleic acids by size.
- The molecules move through the gel due to an electric field.
- Agarose is a polysaccharide derived from seaweed.
Visualization of DNA: Using dyes like GelRed to stain DNA, making it visible under UV light.
Questions (from the slides): Includes true/false questions and an optional question asking about the purpose of agarose gel electrophoresis. A key question asks to identify the incorrect statement in regards to DNA fingerprinting techniques.

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Description

Explore the fundamentals of forensic DNA fingerprinting through this laboratory exercise. Learn about DNA structure, restriction digestion, and the principles of agarose gel electrophoresis. The quiz will test your understanding of the methodology and protocols involved in this essential forensic technique.