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BLAST into the Past to Identify T. Rex's Closest Living Relative

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability Readily available
Cost Low ($20 - $50)
Safety No issues

Abstract

Believe it or not, scientists were recently able to recover tissue from a 68-million-year-old Tyrannosaurus rex fossil! Not only were they able to purify non-mineralized tissue, but they also succeeded in obtaining partial sequence information for protein molecules in the T. rex tissue. In this genomics science fair project, you will use the T. rex's protein sequence to search sequence databases for the its closest living relatives.

Objective

The objective of this genomics science fair project is to determine the closest living relative to the mighty Tyrannosaurus rex, using simple bioinformatics tools.

Credits

David B. Whyte, PhD, Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "BLAST into the Past to Identify T. Rex's Closest Living Relative" Science Buddies. Science Buddies, 11 Oct. 2014. Web. 1 Nov. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Genom_p018.shtml>

APA Style

Science Buddies Staff. (2014, October 11). BLAST into the Past to Identify T. Rex's Closest Living Relative. Retrieved November 1, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Genom_p018.shtml

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Last edit date: 2014-10-11

Introduction

Have you ever noticed that birds have scales on their feet? The reason they have scales is that, technically speaking, they are reptiles, and reptiles have scales. What about the feathers? Feathers are produced by tissues similar to those that produce scales. Also, birds lay eggs like other reptiles. Not only are birds considered reptiles, but scientists now generally agree that birds are, in fact, dinosaurs. Specifically, birds are members of the clade Maniraptora (a clade is a group of animals related by descent from a common ancestor). Maniraptorans all have shared skeletal features, including bone structures in the wrist and forelimb that were first used for grasping, but that were modified into wings during the evolution of birds.

The Maniraptora is the group of theropod dinosaurs. The major Maniraptoran groups include:

  • Aves: The birds, living dinosaurs.
  • Dromaeosaurs: The "raptors," including velociraptor, made famous in the movie Jurassic Park.
  • Troodontids: Non-avian dinosaurs thought by some to be particularly intelligent.
  • Therizinosaurs: Plant-eating theropods.
  • Oviraptors: The fossil record contains evidence that these dinosaurs were devoted parents.

It is important to note that birds are not descended from velociraptors or any of the other maniraptorans. They are all derived from a common ancestor. Birds split from the other members of the group about 150 or so million years ago, in the Jurassic period. The non-avian dinosaurs became extinct over 65 million years ago, but the birds have flourished.

The evidence that birds are dinosaurs is based on detailed studies of fossils, as well as the biology of modern birds. Recently, a new avenue of analysis became available with the extraction of tissue from dinosaur bones. Dr. John Asura, and other scientists, published an account of their analysis of collagen proteins purified from bones of a Tyrannosaurus rex (T. rex) in the journal Science, which you can find in the Bibliography, below. They were able to obtain partial sequence information from the T. rex collagen proteins. Although the protein sequence they obtained is not complete (see the Experimental Procedure, below, for the actual sequence), it is has enough information to allow searching of sequence databases.

T. rex head

Figure 1. T. rex head reconstruction at the Oxford University Museum of Natural History. (Wikipedia, 2006.)

BLAST is a program used to search databases of sequence information. For this science fair project, you will search SwissProt, a database of protein sequences. Each record has the protein sequence, as well as the authors who submitted the sequence, the article associated with the sequence, and other information.

In the Experimental Procedure, you will use BLAST to search the SwissProt protein database for sequences related to the T. rex sequence. If two organisms are descended from a recent common ancestor, their protein sequences will be similar. For example, the collagen genes in two species that split 1 million years ago will have fewer differences than two species that split 10 million years ago. This is because DNA accumulates mutations over time. If the rate at which mutations accumulates is constant, the number of mutations is proportional to the time since the species split. In other words, you can use protein or DNA sequence comparisons to establish how animals are related to each other.

Using BLAST, and publicly available databases, you can perform your own genomics science fair project, studying the evolutionary relationships of various animals. Now that the database contains sequence information for T. rex, you have the tools needed to investigate which of the organisms represented in the SwissProt database is most related to this extinct dinosaur.

Terms and Concepts

  • Clade
  • Maniraptora
  • Evolution
  • Therapod
  • Ave
  • Dromaeosaur
  • Troodontid
  • Therizinosaur
  • Oviraptors
  • Collagen proteins
  • BLAST
  • Mutation
  • Query
  • Fasta format
  • Phylogenetic tree
  • Evolution

Questions

  • What does the acronym BLAST stand for?
  • Based on your research, draw a family tree that includes birds, dinosaurs, reptiles, and mammals.
  • What dinosaurs have been found to have feathers?

Bibliography

These websites offer more information about dinosaurs, specifically those discussed in this science fair project:

These websites are useful resources for understanding how DNA can be used to build evolutionary trees and the bioinformatics tools used to do this:

Materials and Equipment

  • Computer with access to the Internet
  • Lab notebook

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Experimental Procedure

The procedure for this genomics science fair project has three sections: 1) Obtain the Tyrannosaurus rex sequence data to use as a query (the query sequence is used to search the database), 2) Use BLAST to search SwissProt, an online database of protein sequences, for the best match to the T. rex sequence, and 3) Build a tree graphically showing the relationship of T. rex to its living relatives.

  1. The partial sequence for the Tyrannosaurus rex collagen protein is pasted below. It is from the Science article by Asara, listed in the Bibliography. Regions where the protein sequence is not known have hyphens (---). The capital letters each represent an amino acid in the protein sequence. Note that most of the protein was not successfully sequenced, but considering that the tissue was 68 million years old, it is remarkable any sequence was obtained. The protein sequence is in fasta format, which means that the sequences are preceded by a header line that starts with a ">" and ends with a return, or a new paragraph. The fasta format is the standard formatting used by bioinformatics software.
    >Tyrannosaurus rex, collagen type I, alpha 1 
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    --------------------------GATGAPGIAGAPGFPGARGAPGPQGPSGAPGPK-----------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------GVQGPPGPQGPR------------------------------------------------------
    ----------------------------------------------------------------------------
    --------------------------------------GSAGPPGATGFPGAAGR---------------------
    -------------------------------------------------------GVVGLPGQR------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    ----------------------------------------------------------------------------
    -------------------------------GLPGESGAVGPAGPPGSR--
    
  2. Copy the sequence of the T. rex collagen protein above, including the header line (>Tyrannosaurus rex) and all of the hyphens.
  3. Open a BLAST page at the National Center for Biotechnology Information (NCBI).
    1. Go to the NCBI main page: http://www.ncbi.nlm.nih.gov/
    2. Click on BLAST to go to the BLAST page.
    3. Under "Basic BLAST," click on "protein BLAST."
  4. Paste the T. rex sequence into the "Enter Query Sequence" box.
  5. For job title, use "Tyrannosaurus rex."
    1. If you kept the header line (>Tyrannosaurus rex) at the top of the sequence, it will be added here automatically.
  6. Under "Database," choose the SwissProt protein database.
  7. In the box for "Entrez Query," type "COL1A1 [GENE] AND 1400:1500 [SLEN]".
    1. COL1A1 [GENE]: This limits the search to collagen type 1, alpha 1, which is the collagen type for the T. rex sequence. Otherwise, the BLAST result lists hits with other collagen types.
    2. 1400:1500 [SLEN]: This limits the BLAST output to sequences between 1400 and 1500 amino acids. Otherwise, BLAST finds small partial sequences.
  8. Leave the box for "Organism" empty.
  9. Under "Algorithm," select blastp (protein-protein BLAST).
  10. Click on the BLAST button on the bottom of the page to begin the search.
    1. If you would like to explore BLAST options, click on "Algorithm Parameters."
  11. Be patient. It will take a few minutes for the screen to appear. The BLAST results page will appear when the search is complete. See Figure 2, below, for a snapshot of the output page.
  12. What organism is most related to T. rex, based on similarity of collagen genes?
    1. Note: As more sequences are added to the database, the list of hits will increase.
BLAST page of T. rex

Figure 2. BLAST output page. Note the "Score" column. Genes with the highest score are most related to the T. rex query sequence. The E value is an estimate of the chance that the sequences are not related. The lower the E value, the more certain the sequences are related. Below the list of hits are the alignments of the T. rex amino acid sequence with the sequences in the database. Note the "Identities" value, which is the percent of amino acids that are the same in the query and the database sequence. "Positives" measures the percent of amino acids that remain the same or that were changed into similar amino acids. (NCBI, 2008.)

  1. Make a table based on the BLAST output. List the organism's scientific name, common name, the score, and the E value.

In this section, you will use the BLAST output to make a tree that graphically depicts the degree of similarity of the proteins. There are more sophisticated ways to generate a phylogenetic tree, which you can explore in the Variations section, below.

  1. Click on "Distance tree of results" to generate a tree of the BLAST results.
    1. This will create a tree in "rectangular" format.
  2. Select "Fast minimum evolution" for tree method.
  3. Leave "Max sequence difference" at the default value of 0.85.
  4. Click on "Grishin General (protein)" for the "Distance" parameter.
  5. Click on the "Force" tab to create a tree like the one in Figure 3.
  6. For "Sequence Label," select "Taxonomic Name."
Tree of BLAST hits: T. rex collagen

Figure 3. Tree based on BLAST results of Tyrannosaurus rex protein sequence against the SwissProt database of protein sequences. (NCBI, 2008.)

  1. Add the common name for each species to the tree.
    1. This might be easier if you redraw the tree by hand or use a computer graphics program.
  2. Add BLAST data, such as the % identity, to the tree.

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Variations

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