DNA Profiling Techniques in Criminology

Oct 3, 2024

Lecture Notes: DNA Profiling in Criminology

Introduction

  • Focus on DNA profiling techniques in criminology
  • DNA profiling helps identify individuals by their unique DNA properties

Techniques Explored

  1. Polymerase Chain Reaction (PCR)

    • Amplifies DNA; makes many copies from a single DNA molecule
    • Widely used in COVID-19 testing and other biological applications

    How PCR Works

    • Requires a DNA template or RNA (converted to DNA)
    • Needs nucleotides, primers, and polymerase (specifically Taq polymerase)
    • Taq Polymerase: Temperature-dependent, withstands high temperatures

    PCR Cycle Steps

    1. Denaturation: Heat to ~95°C to split DNA strands
    2. Annealing: Cool to ~60°C so primers bind to DNA
    3. Extension: Polymerase binds and replicates DNA
    • Repeated for 20-30 cycles, exponentially increasing DNA copies

  2. Gel Electrophoresis

    • Used for DNA fingerprinting
    • Separates DNA fragments by size using a porous gel and electrical current

    Process Overview

    • Involves restriction enzymes cutting DNA at specific restriction sites
    • DNA fragments are separated in a gel electrophoresis chamber
    • DNA moves towards positive electrode due to its negative charge
    • Smaller DNA fragments move faster and further through the gel

    Gel Preparation and Loading

    • Gel made from agarose, which forms pores upon cooling
    • DNA loaded into wells with a micro pipet
    • DNA is dyed to visualize it in the gel

    Result Analysis

    • DNA bands compared to a marker for size reference
    • Fluorescent dyes used for visualization

Applications

  • Crime scene analysis: DNA comparison from crime scenes to suspects
  • Paternity/maternity tests
  • Organ donation compatibility
  • Diagnosing genetic disorders
  • Testing for pathogens in food
  • Determining if organisms are genetically modified

Conclusion

  • PCR and gel electrophoresis are crucial in criminology
  • Simple, powerful tools to analyze DNA in various contexts
  • Practical application in lab settings and research labs like the University of Minnesota
  • Connection to broader biological applications

These notes cover the key points of DNA profiling techniques discussed in the lecture, particularly focusing on PCR and gel electrophoresis and their applications in criminology and beyond.