Forensic DNA Analysis in Crime Scene Investigation

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Questions and Answers

What is NOT true about the process of agarose gel electrophoresis?

The process can visualize RNA fragments. (correct)

It allows DNA fragments to move towards the positive electrode.

Larger DNA fragments move more slowly through the gel.

It involves the use of restriction enzymes to cut DNA.

Which statement about restriction enzymes is incorrect?

They create fragments of various lengths for analysis.

Different enzymes recognize different DNA sequences.

All restriction enzymes cut DNA at the same sequence. (correct)

They can be used to cut DNA at specific sequences.

In the context of gel electrophoresis, what does the term 'ladder' refer to?

A type of gel medium used for electrophoresis.

An equipment setup that helps to stabilize the gel.

A tool used to measure DNA concentration.

A mix of DNA fragments of known sizes used for comparison. (correct)

What is the role of the UV transilluminator in gel electrophoresis?

It visualizes the DNA fragments for documentation. Signup and view all the answers

Why is it important to cover the electrophoresis chamber with a lid during the process?

To ensure proper contact between the electrodes. Signup and view all the answers

What is the primary purpose of using a loading dye during agarose gel electrophoresis?

To track the progress of the electrophoresis process Signup and view all the answers

Which component is essential for the staining and visualization of DNA in agarose gel electrophoresis?

GelRed Signup and view all the answers

At what temperature should the DNA samples be incubated after adding the enzyme mix?

37°C Signup and view all the answers

What is the role of agarose in the electrophoresis process?

To provide a matrix for the separation of nucleic acids Signup and view all the answers

What step must be performed after melting the agarose to prepare the gel?

Pour the agarose into a casting tray Signup and view all the answers

Which of the following accurately describes the migration direction of DNA in agarose gel electrophoresis?

Toward the anode (+) due to its negative charge Signup and view all the answers

What is the correct concentration of agarose in the gel preparation described?

1.0% Signup and view all the answers

Which action should NOT be performed when mixing the DNA samples with the enzyme mix?

Pipetting vigorously to ensure even mixing Signup and view all the answers

What is the primary purpose of DNA fingerprinting in the context of a criminal investigation?

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

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

It results from variations in DNA sequences recognized by restriction enzymes Signup and view all the answers

During the DNA analysis process, which step directly follows the restriction digest of the DNA samples?

Agarose gel electrophoresis Signup and view all the answers

Which statement is true regarding the preparation of the agarose gel for electrophoresis?

The gel concentration can affect the resolution of DNA fragments Signup and view all the answers

What type of biological evidence was collected from the crime scene to aid in the investigation?

DNA from skin cells under the victim's fingernails Signup and view all the answers

In the context of the investigation, which group of individuals are considered suspects?

Individuals who were familiar with the victim's schedule Signup and view all the answers

What is the expected outcome after performing a comparison of the DNA fragments from the suspects and the victim?

To reveal the murderer based on matching patterns Signup and view all the answers

What is a crucial feature of the genomic site involved in RFLP analysis?

Its length may range from four to eight nucleotides in polysomic regions Signup and view all the answers

Study Notes

Forensic DNA Fingerprinting

Theoretical Background:
- Introduction to DNA fingerprinting
- Restriction digest of DNA samples
- Principle of agarose gel electrophoresis
Methodology and Protocol:
- Sample and agarose gel preparation
- Electrophoresis of DNA samples
- Analysis and interpretation of results

The Crime

A medical student from European University Cyprus was found dead at the university parking lot.
The student was murdered.
The CSI Nicosia Department asked fellow medical students for assistance in finding the murderer.

The Clues

Evidence suggests a violent struggle at the crime scene.
DNA was collected from under the victim's fingernails.

The Suspects

There are five suspects: the heartbroken ex-girlfriend, the jealous brother, the girlfriend, the campus security guard, and the father of the heartbroken ex-girlfriend.

The Plan

The students worked together to solve the crime.
They reviewed the procedures they learned and determined a solution.
DNA from the suspects was isolated and compared to the DNA from the crime scene using the RFLP technique.
DNA fingerprinting connects biological evidence to suspects in criminal investigations.

Restriction Fragment Length Polymorphism (RFLP)

A type of polymorphism caused by variations in DNA sequences recognized by restriction enzymes.
Short genomic sites (4-8 nucleotides) that differ among individuals are polymorphic.
DNA is treated with restriction enzymes that cut the DNA into fragments of various lengths.
Resulting fragments are separated by length, creating a unique pattern for each individual.

Experimental Procedure (Part A: Restriction Digest)

10 µl of DNA sample from each suspect and crime scene are transferred to labelled tubes.
10 µl of enzyme mix was added to each respective tube.
The tubes are mixed (flicking gently).
Tubes are placed in a 37°C water bath for 45 minutes

Experimental Procedure (Part B: Agarose Gel Electrophoresis and Visualization of DNA Fragments)

A 1% agarose gel is prepared using 100 ml of TAE buffer and 1 g of agarose in an Erlenmeyer flask.
The agarose is melted in a microwave or on a heat source, and periodically swirled to avoid boiling.
The gel is poured into a casting tray and allowed to solidify.
The comb is removed and the gel is placed in an electrophoresis chamber filled with buffer solution.
20 µl of dye sample is loaded into each well.
Electrophoresis is performed for 40 minutes at 100-120V.
The gel is visualized using a UV transilluminator, and the results are documented and interpreted by the students and instructor.

Experimental Procedure - DNA Samples should contain:

The following DNA samples and volumes are used
- Crime Scene (CS) - 10 µl
Suspect 1 (S1) - 10 µl
Suspect 2 (S2) - 10 µl
Suspect 3 (S3) - 10 µl
Suspect 4 (S4) - 10 µl
Suspect 5 (S5) - 10 µl
For each sample - 20 µl of Eco/Pst enzyme mix.

RFLP Markers Inheritance & Test Validity

Diagram showing inheritance patterns of RFLP markers and potential genotypes (AA, aa, Aa) among family members (parents and siblings)

Agarose Gel Electrophoresis Principle

Agarose Gel electrophoresis is used to separate nucleic acids by size.
Nucleic acids migrate through an agarose gel due to an electric field (cathode- to anode+).
Agarose is a polysaccharide extracted from seaweed.
DNA is visualized using dyes like GelRed, which bind to DNA and fluoresce under UV light.
A tracking dye is mixed with the sample to monitor its movement.

Questions:

Which of the following is FALSE? – Option D
What is the purpose of Agarose Gel Electrophoresis? – Option (C)

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Description

Explore the intricate process of forensic DNA fingerprinting while helping medical students solve a murder case at the European University Cyprus. This quiz covers the theoretical background, methodology, and analysis of DNA samples as students work together to identify the murderer among five suspects. Test your knowledge of forensic science and criminal investigation techniques.