Phylogenetic Analysis

INTRODUCTION

The theory of evolution is the foundation upon which all of modern biology is built. From anatomy to behavior to genomics, the scientific method requires an appreciation of changes in organisms over time. It is impossible to evaluate relationships among gene sequences without taking into consideration the way these sequences have been modified over time. Evolutionary theory states that groups of similar organisms are descended from a common ancestor. Phylogenetic systematics (cladistics) is a method of taxonomic classification based on their evolutionary history. It was developed by Willi Hennig, a German entomologist, in 1950.

Molecular phylogenies are inferred from molecular (usually sequence) data either cladistics (e.g. gene order) or phonetic. Evolutionary relationships are documented by creating a branching structure, termed a phylogeny or tree, which illustrates the relationships between the sequences. Cladistic methods construct a tree (cladogram) by considering the various possible pathways of evolution and choose from among these the best possible tree.

A phylogram is a tree with branches that are proportional to evolutionary distances.

Phylogenetic Analysis is the study of evolutionary relationships among organisms.  The purpose of a phylogenetic tree is to illustrate how a group of objects (usually genes or organisms) are related to one another.

CLASSES OF ALGORITHM USED TO INFER PHYLOGENY FROM SEQUENCE

• Distance methods

• Parsimony

• Likelihood

• Probabilistic methods

There are two types of approaches to phylogenetic tree construction:-

Cladistic vs. Phenetic

Within the field of taxonomy there are two different methods and philosophies of building phylogenetic trees: cladistic and phenetic

Phenetic methods construct trees (phenograms) by considering the current states of characters without regard to the evolutionary history that brought the species to their...