Skip to content Skip to navigation

Connexions

You are here: Home » Content » Current Research: DNA Barcode Results

Navigation

Content Actions
  • Download module PDF
  • Add to ...
    Add the module to:
    • My Favorites
    • A lens
    • An external social bookmarking service
    • My Favorites (What is 'My Favorites'?)
      'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.
    • A lens (What is a lens?)

      Definition of a lens

      Lenses

      A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

      What is in a lens?

      Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

      Who can create a lens?

      Any individual Connexions member, a community, or a respected organization.

    • External bookmarks
  • E-mail the author

Recently Viewed

This feature requires Javascript to be enabled.

Current Research: DNA Barcode Results

Module by: Alison Fromme

Summary: Hebert et al 2004 studied birds to determine whether or not a standard section of DNA could distinguish between species. Their results are summarized here.

hebert-fig1.bmp

Interpreting Results

Figure 1: Figure 1. Comparison of Nucleotide Sequence Differences in COI among 260 Species of North American birds Adapted from: Hebert PDN, Stoeckle MY, Zemlak TS, Francis CM (2004) Identification of Birds through DNA Barcodes. PLoS Biol 2(10): e312.
Comparison of DNA differences among North American Birds
Comparison of DNA differences among North American Birds (Barcode-Figure-1.gif)

The original research paper states: "Pairwise comparisons between 437 COI sequences are separated into three categories: differences between individuals in the same species, differences between individuals in the same genus (not including intraspecific differences), and differences between individuals in the same family (not including intraspecific or intrageneric differences)."

What does the figure mean? Researchers used the DNA sequence from the COI gene in birds to figure out if the COI gene is useful as a DNA barcode-- in other words, a unique identifier for bird species.

For the "Within Species" analysis (top panel), researchers compared one bird's 640-base pair COI sequence with another sequence from a bird of the same species. They recorded the number of differences between the two sequences (identical sequences would have zero differences, whereas completely different sequences would have 640 differences).

They repeated this for all of their bird sequences. These comparisons are called "pairwise" because the data they recorded was based on each pair of sequences compared. In the graph, the x-axis shows the number of differences between sequences, and the y-axis shows the percentage of comparisons.

For the "Within Genus" analysis (middle panel), researchers compared one bird COI sequence with all the others of the same genus. Again, they recorded the number of differences between the sequences, and then repeated this analysis for all the sequences. Since members of the same genus might also be members of the same species, they didn't count those comparisons. The same method was used for "Within Family" comparisons.

Problem 1: What percentage of pairwise comparisons within species found zero differences?
0%
94%
0.43%
Problem 2: Estimate the average number of sequence differences within species.
About 94
About 8
Less than 1

Problem 3: Which group had the least amount of sequece variation at this gene?
Family
Genus
Species
Problem 4: COI sequence comparisons within families had between:
0-8 differences.
1-16 differences.
5-20 differences.
Problem 5: Which of the following statements best supports the use of the COI gene as a barcode to identify species?
94% of comparisons within species found zero differences.
The average number of differences for within genus comparisons was 7.93.
The average number of differences for within family comparisons was 12.71.

Your turn...

  • How does this graph support the use of DNA barcodes to identify species?
  • What about the 6% of individuals that did differ from others in the same species?
  • Is there any other information would you want to know before using DNA barcodes to identify species?

Source

Identification of Birds through DNA Barcodes

Paul D. N. Hebert1* , Mark Y. Stoeckle2 , Tyler S. Zemlak1 , Charles M. Francis3

1 Department of Zoology, University of Guelph, Guelph, Ontario, Canada, 2 Program for the Human Environment, Rockefeller University, New York, New York, United States of America, 3 National Wildlife Research Centre, Canadian Wildlife Service, Ottawa, Ontario, Canada

DOI: 10.1371/journal.pbio.0020312 Copyright: © 2004 Hebert et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Citation: Hebert PDN, Stoeckle MY, Zemlak TS, Francis CM (2004) Identification of Birds through DNA Barcodes. PLoS Biol 2(10): e312.

Comments, questions, feedback, criticisms?

Send feedback