September 5, 2009

Phylogenetic Trees: An Introduction

Filed under: Bioinformatics,Computational Biology — Biointelligence: Education,Training & Consultancy Services @ 3:01 am
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The term phylogeny refers to the evolution or historical development of a plant or animal species, or even a human tribe or similar group. A phylogenetic tree is a graphical representation of the evolutionary relationship between biological groups.

A phylogenetic tree is a specific type of cladogram where the branch lengths are proportional to the predicted or hypothetical evolutionary time between organisms or sequences. Cladograms are branched diagrams, similar in appearance to family trees, that illustrate patterns of relatedness where the branch lengths are not necessarily proportional to the evolutionary time between related organisms or sequences.Below is shown a Cladogram as an example.


Cladograms can rely on many types of data to show the relatedness of species. In addition to sequence homology information,

comparative embryology, fossil records and comparative anatomy are all examples of the types of data used to classify species

into phylogenic taxa. So, it is important to understand that the cladograms generated by bioinformatics tools are primarily

based on sequence data alone.It only illustrates the probability that two organisms, or sequences, are more closely related

to each other than to a third organism, it does not necessarily clarify the pathway that created the existing relationships. 


There are varius tools available in the bioinformatics research community for phylogenetic analysis. Here are some popular

tools listed below:
1. Phylip (
2. MEGA (
3. PAUP (
4. PhyloDraw (