🧬

DNA Barcoding Lecture Insights

May 8, 2025

Lecture Notes on DNA Barcoding by Dr. John James Wilson

Introduction

  • Speaker: Dr. John James Wilson, Curator of Vertebrate Zoology at World Museum, National Museums Liverpool.
  • Location: Typically based at World Museum; currently working from home.
  • Collection: Manages vertebrate zoology collection; includes about 80 specimens of birds, mammals, fish, reptiles, and amphibians.
    • Bird collection: 2nd largest in the UK with specimens over 150 years old.

Importance of Taxonomy and Biodiversity

  • Estimated 10 to 15 million animal species on Earth; only 1.5 million described.
  • Requires around 15,000 taxonomists for effective species identification globally.
  • Taxonomic Impediment: Lack of taxonomic expertise hampers species identification.

DNA Barcoding

  • Origin: Idea from Canadian professor Paul Hebert; inspiration from supermarket barcodes.
  • Definition: DNA barcoding uses short sequences of DNA to identify species.
  • Popularization: Paul Hebert popularized the term and methodology.

DNA Barcoding Mechanism

  • DNA Structure: DNA is a double helix made of nucleotide bases (A, C, G, T).
  • Focus on Mitochondrial DNA: Mitochondrial DNA is simpler (37 genes) than nuclear DNA (20,000-25,000 genes).
    • CO1 Gene: Cytochrome c oxidase subunit 1 (CO1) gene, approximately 658 base pairs long, is used as a barcode for animals.

Process of DNA Barcoding

  1. DNA Extraction:
    • Cell lysis (breaking open cells), purification of DNA using filters.
    • Commercial kits are available for DNA extraction.
  2. PCR (Polymerase Chain Reaction):
    • Amplifies the CO1 gene fragment using primers, nucleotides, and polymerase enzyme.
    • Involves thermal cycling to create millions of copies of the target DNA.
    • Commercial kits available for PCR as well.
  3. DNA Sequencing:
    • Sanger Sequencing: Used for obtaining the DNA sequence of the amplified product.
    • Fluorescent nucleotides mark the sequence, producing a chromatogram indicating base pairs.
  4. Sequence Editing:
    • Manual checking of chromatogram peaks to ensure accuracy in nucleotide calls.
  5. Comparison and Identification:
    • Compare unknown specimen's barcode to a reference library (BOLD system) for identification.
    • If no match, a Barcode Index Number (BIN) is assigned for future reference.

Advancements in Field DNA Barcoding

  • Portable lab equipment being developed for field use (e.g., Vento Lab).
  • Allows for DNA barcoding directly in the field.

Applications of DNA Barcoding

  • Environmental DNA: Used for species monitoring without capture.
    • Example: Detecting Southern River Terrapin DNA in river water.
  • Invertebrate-derived DNA: Detecting mammal DNA using blow fly gut contents.
  • DNA Metabarcoding: High-throughput sequencing of mixed species samples (e.g., Malaise traps).

Local Involvement in DNA Barcoding

  • UK lags behind in building DNA barcode libraries.
  • Workshops conducted to engage local recorders and enthusiasts in DNA barcoding.
  • Darwin Tree of Life Project: Efforts to sequence UK multicellular life and build a DNA barcode library.

Conclusion

  • DNA barcoding is a powerful tool for species identification and biodiversity studies.
  • Encourages participation from local communities in species recording activities.

Questions

  • Discussion on various aspects such as the preservation of specimens, cross-contamination, primer use, and metagenomics followed the presentation.

Full transcript