Evolutionary relationships, phylogenetic trees and finding new drugs


How can understanding phylogenetic trees and the evolutionary relationships between species lead to the discovery of new drugs for Alzheimers and other diseases?

These resources for post-16 students introduce evolutionary relationships and phylogenetic trees, putting it in the context of modern drug discovery. Topics covered include creating a phylogenetic tree, using DNA and protein sequences to determine evolutionary relationships, and identifying possible sources of new drugs. The resources include teachers’ guide, students’ worksheets and a Powerpoint.

This topic will span two lessons, with students tackling the creation of a phylogenetic tree as a homework challenge.

A phylogeny, phylogenetic tree, or evolutionary tree is a diagram showing the evolutionary relationships between a group of organisms. Closely related species are likely to have similar characteristics, with some differences. Thus, if one species is known to have certain characteristics, such as containing beneficial drugs, it is reasonable to suppose that closely related species may contain similar drugs.

The Narcissus (daffodil) genus is one plant family that contains these potentially life-saving drugs. Papers have been published about the search for Alzheimer’s treatments (Rønsted et al., 2010) and anti-viral drugs (Ooi et al., 2010) in the genus Narcissus. There has also been a paper on the evolution of stylar polymorphisms in this genus (Graham and Barrett, 2004). These papers are freely available online. Some DNA and protein sequences have been determined for several species of Narcissus and these have been used to try to understand the evolutionary relationships of species within this genus.

These resources use a 162 Amino acid sequence of a fragment of the protein NADH dehydrogenase subunit F. Sequence data from Uniprot (www.uniprot.org) provided 41 records for species and subspecies of Narcissus (some species are duplicated) and 3 out-group species (Galanthus nivalis, Leucojum aestivum and Lapiedra martinezii).

To find the original data (freely available online) go to www.uniprot.org and do an advanced search to include the protein name, sequence length and genus (or out-group species name). The “basic data” word and excel documents include all these sequences identified with species name and year.

This resource was developed by Chris Graham, Course Team Leader for Biology at Long Road Sixth Form College, Cambridge, funded by a SAPS Associate Award.

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