PCR in Forensic Science: A Powerful Tool

-

 

PCR in Forensic Science: A Powerful Tool

Introduction

Forensic genetics leverages genetic tools and scientific methods to solve legal cases, both criminal and civil. The principle of Locard’s Exchange posits that every contact leaves a trace, making any evidence crucial in forensic analysis. Biological evidence found at crime scenes can include cellular material or cell-free DNA. As genetic technologies have advanced, these methods have been applied to both human and non-human genetic analyses.

DNA Profiling Techniques

Two primary techniques are used for DNA fingerprinting in forensic science:

  1. Restriction Fragment Length Polymorphism (RFLP):
    • The first approach used for DNA profiling.
    • Not commonly used due to its time-consuming nature and requirement for high-quality DNA.
    • Involves cutting DNA with restriction enzymes and analyzing the resulting fragments.
    • Less practical for routine forensic analysis.
  2. PCR-based Variable Number Tandem Repeat (VNTR) or Short Tandem Repeat (STR) Determination:
    • More commonly used due to its sensitivity and efficiency.
    • Utilizes PCR to amplify a small amount of DNA.
    • VNTRs consist of 17-19 base pair repeat sequences, while STRs consist of 2-4 base pair repeat sequences.
    • Several different STRs are amplified by PCR and analyzed by DNA sequencing.
    • Currently the most commonly used method in forensic science.

Organization of DNA

In every human nucleated cell, there are two complete copies of the genome. The human genome comprises around 3.2 billion base pairs arranged into 23 pairs of chromosomes. Here’s a breakdown:

  1. Genes (1.5% of the genome):
    • Encode and regulate protein synthesis.
    • Estimated to contain between 20,000 to 25,000 genes.
  2. Noncoding regions (23.5% of the genome):
    • Do not encode proteins but play a role in gene expression regulation.
    • Include enhancers, promoters, repressors, and polyadenylation signals.
  3. Extragenic DNA (75% of the genome):
    • Composed of repetitive DNA.
    • Interspersed repeats (50%):
      • Short interspersed elements, long interspersed elements, long terminal repeats, and DNA transposons.
    • Tandem repeats (45%):
      • Satellite DNA, minisatellite DNA, and microsatellite DNA.

PCR’s Role in Forensic DNA Analysis

PCR is a critical technique in forensic DNA analysis. Its main advantages include:

  1. Amplification of DNA:
    • PCR allows forensic scientists to amplify or make copies of regions of the genome that vary widely between different individuals (VNTRs or STRs).
    • By comparing the length of different VNTRs or STRs, scientists can determine whether a sample matches a suspect’s DNA.
  2. Applications:
    • Identifying suspects or victims.
    • Exonerating wrongfully accused individuals.
    • Linking crimes together through DNA evidence.

Remember, PCR’s power lies in its ability to amplify small amounts of DNA, making it an indispensable tool for forensic investigators. 🧬🔍

 

Comments

Post a Comment

Popular posts from this blog

The Secrets of Ecosystems: Unveiling Nature’s Harmonious Web

-
Image
An ecosystem is more than just a collection of plants, animals, and landscapes. It’s a complex web of interactions where life forms and their environment coexist in delicate balance. In this blog, we’ll talk about ecosystems, exploring their structure, components, and vital functions and impact on human health. What is an Ecosystem? An ecosystem is a structural and functional unit of ecology . Its where living organisms interact with each other and their surroundings. Picture it as a grand symphony, with each species playing a unique role, contributing to the overall harmony. Structure of the Ecosystem Biotic Components Producers (Autotrophs) : These green virtuosos, mainly plants, harness sunlight through photosynthesis to create their own food. They form the foundation of the food chain, nourishing all other organisms. Consumers (Heterotrophs) : Primary Consumers : Herbivores that feast on producers. Secondary Consumers : Carnivores or omnivores tha...
Read more

BIOCHEMICAL TESTS: IDENTIFICATION OF BACTERIAL ISOLATES AND DIFFERENT BACTERIAL SPECIES

-
Image
Biochemical tests are essential in microbiology for identifying and characterization of microorganisms.                                                               Image source: chegg.com Carbohydrate Fermentation Test : Microorganisms use carbohydrates differently based on their enzyme components. In fermentation, substrates and alcohols undergo anaerobic dissimilation, producing organic acids (e.g., lactic acid, formic acid, or acetic acid). Phenol Red indicator detects acid production (red at neutral pH 7, turns yellow at slightly acidic pH 6.8). Gas production (e.g., hydrogen or carbon dioxide) can also accompany acid production. Procedure : Inoculate a carbohydrate fermentation broth with the test microorganism. Incubate at 37°C for 24...
Read more

Threat of Bird Flu: Is It the Next Pandemic?

-
Image
              Image Source:The Guardian   In recent times, the world has been grappling with a silent menace—the avian influenza, commonly known as bird flu. While COVID-19 has dominated headlines, bird flu has been quietly spreading its wings, raising concerns among scientists and health experts. In this blog, we delve into the intricacies of bird flu, its potential impact, and why it warrants our attention. What Is Bird Flu? Bird flu, scientifically referred to as avian influenza, is caused by infection with avian influenza Type A viruses (H5N1), A (H7N9), and A (H9N2). These viruses naturally circulate among wild aquatic birds and can also infect domestic poultry and other bird species. While bird flu primarily affects birds, sporadic cases of human infections have occurred. Symptoms: ·        Typical Flu-Like Symptoms ·        Respiratory Symptoms ·    ...
Read more