Barcoding Overview

Question 1

History of barcoding

Answer 1

1. Early 80s = DNA cloned from ssDNA and cDNA
   - long and expensive
2. 1st genomes from plant (2000) and human (2001)
   - ~ 250 authors
   - took years and expensive
3. Today can sequence genomes and RNA
   - in an afternoon
   - ~£500

Question 2

Wellcome Sanger institute

Answer 2

• Most famous genome sequencing institute
• Wants to sequence 66,000UK species to further - understanding
• existed for 25 years
• can request certain species e.g. Cardiff W/ otters
• some invasive e..g. Brambles that are asexual

Question 3

Uses of DNA barcoding

Answer 3

1. Taxonomy
2. Systematics (relationships among species)
3. Biodiversity (variability between orgs)
   E.g. fish markets (often are missold as more desirable/expensive fish) allows to actually identify
   E.g. forensic science. Even used with pollen grain DNA.

Question 4

How barcoding is done

Answer 4

1. Plants sampled and DNA extracted
2. Barcode chosen
3. barcode PCR amplified
4. DNA sequenced (3-4 days)
5. Returned with section of DNA sequence thats barcode
6. Compare with similar organisms in data base to see if evolution can be suggested

Question 5

Problems with barcoding

Answer 5

1. Unknown number of species
   E.g. fungi
   - most don’t even know we are losing

2. Defining a species is complex 
Relies of many factors such as:
- interbreeding capabilities 
- morphological variation 
- ecological niche 
- genetic similarities/dissimilarities

Question 6

Criteria for DNA barcode

Answer 6

Universality (primers that amplify consistently)
Robustness
Level of discrimination (different from other sequences)

Question 7

Plant vs animal barcoding

Answer 7

Easier with animals
- mitochondrial cytochrome C oxidase (CO1)
Chloroplast genes rbcl and matK similar
Also highly conserved is internal transcribe spacer regions 1 and 2 (ITS)
- mutations dont alter plant so much = more areas that are highly specific to plant

Question 8

The future of barcoding?

Answer 8

There will be universal reference database

Usable by specialists