Ahmedabad Air India Crash – "DNA Profiling" Nearly Complete

What is DNA Profiling? 

DNA profiling is a scientific method used to identify a person based on their unique DNA.

• Just like everyone has a unique fingerprint, everyone (except identical twins) has unique DNA.

• DNA is found in cells (like blood, hair, saliva, skin).

• A small part of DNA has patterns that are unique to every individual.

• These unique patterns are studied to match or identify a person.

Process of DNA Profiling (Step-by-step )

1. Sample Collection:

   • DNA is taken from sources like blood, saliva, semen, hair, or bones.

2. DNA Extraction:

   • DNA is separated and purified from the sample.

3. Amplification (PCR):

   • Using a technique called PCR (Polymerase Chain Reaction), specific DNA regions are copied many times to make enough to study.

4. Fragment Analysis:

   • Special parts of DNA (called STRs – Short Tandem Repeats) are analyzed, which differ from person to person.

5. DNA Profile Creation:

   • A graph or pattern is generated showing the DNA features of the person.

6. Comparison/Matching:

   • The profile is compared with others — for example, to match a crime suspect, find missing persons, or establish parentage.

 UPSC Prelims Points:

• DNA Profiling = Technique to identify individuals using DNA.

• PCR (Polymerase Chain Reaction) = Used to amplify DNA.

• STRs (Short Tandem Repeats) = Part of DNA used for comparison.

• Applications:

  • Forensic investigations

  • Disaster victim identification

  • Paternity testing

  • Missing persons tracing

• DNA is not present in ribosomes – Ribosomes are composed of ribosomal RNA (rRNA) and proteins, not DNA.(also Human RBC don't have DNA)

• DNA’s Role: Stores genetic instructions for building and maintaining an organism.

• Ribosomes’ Role: Synthesize proteins using mRNA (transcribed from DNA).

• Where DNA is Found:

  • Nucleus (primary location in eukaryotic cells).

  • Mitochondria (have their own DNA).

  • Chloroplasts (in plant cells, contain their own DNA).

• While DNA provides the genetic code, ribosomes (which lack DNA) translate that code into proteins.

Is DNA Found in Red Blood Cells (RBCs)?

• • Mature RBCs (in humans & mammals): No DNA

    • They lose their nucleus and organelles (including mitochondria) during maturation to maximize hemoglobin content for oxygen transport.

    • Since they lack a nucleus and mitochondria, they do not contain any DNA.

  • Immature RBCs (reticulocytes): Temporarily retain some organelles

    • Early-stage RBCs still have ribosomal RNA (rRNA) but no nuclear DNA.

    • Any remaining DNA fragments are degraded before full maturation.

  • Exceptions:

    • Birds & some reptiles have nucleated RBCs (contain DNA).

    • Fetal RBCs in early development (in mammals) may briefly contain nuclei.

• Mature human red blood cells do not contain DNA, making them useful in DNA forensics (since any DNA in blood samples comes from white blood cells, not RBCs).