Using Bioinformatics to Investigate Evolutionary
Relationships; Have a BLAST!
Introduction:
Between 1990-2003, scientists working on an international research project known as the
Human Genome Project, were able to i
...
Using Bioinformatics to Investigate Evolutionary
Relationships; Have a BLAST!
Introduction:
Between 1990-2003, scientists working on an international research project known as the
Human Genome Project, were able to identify and map the 20,000 – 25,000 genes that
define a human being. The project also successfully mapped the genomes of other species,
including the fruit fly, mouse and Escherichia coli. The location and complete sequence of the
genes in each of these species are available for anyone in the world to access via the Internet.
Why is this information important? Being able to identify the precise location and sequence of
human genes will allow us to better understand genetic diseases. In addition, learning about
the sequence of genes in other species helps us understand evolutionary relationships among
organisms. Many of your genes are identical of similar to those found in other species.
Suppose you identify a single gene that is responsible for a particular disease in fruit flies. Is
that same gene found in humans? Does it cause a similar disease? It would take you nearly 10
years to read through the entire human genome to try to locate the same sequence of bases as
that in fruit flies. This definitely isn’t practical, so a sophisticated technological method is
needed.
Bioinformatics is a field that combines statistics, mathematical modeling, and computer
science to analyze biological data. Using bioinformatics methods, entire genomes can be
quickly compared in order to detect genetic similarities and differences. An extremely powerful
bioinformatics tool is BLAST, which stands for Basic Local Alignment Search Tool. Using
BLAST, you can input a gene sequence of interest and search entire genomic libraries for
identical or similar sequences in a matter of seconds.
In this investigation, you will use BLAST to
compare several genes, and then use the
information to construct a cladogram. A
cladogram (also called a phylogenetic tree)
is a visualization of the evolutionary
relatedness of species. Figure 1 to the
right is a simple cladogram.
Note that the cladogram is treelike, with
the endpoints of each branch representing
a specific species. The closer the two
species are located to each other, the
more recently they share a common
ancestor. Figure
1: A simple cladogram of the Phylum Chordata.
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