How do we use the principles of max parsimony and max likelihood to construct tr

Question

How do we use the principles of max parsimony and max likelihood to construct trees? How do they lend support to our trees? Why are trees helpful? Define and give examples of orthologous and paralogous genes. How are they formed? How do these help us trace evolutionary histories and make molecular clock estimates using neutral theory? We have recently learned about microbes that can use Arsenic in place of Phosphorus in biomolecules including DNA, proteins and ribosomes. Much of the media hype surrounding this finding has proposed that this is a "new life form!" How could you determine whether in fact this is a new form of life? What gene(s) would you use to build your tree? Is it likely that this represents new life? What do you think is most likely? A tree of life? A ring of life? A web of life? How does horizontal gene transfer influence your opinion?

Explanation / Answer

A tree diagram that shows pattern of evolution of a group of organism based on their genetic of phenotypic characters with respect to the time is called phylogenetic tree. It is also called evolutionary tree and it explains the evolutionary interactions and how organisms evolved from a common ancestor. There are different types are trees can be constructed based on the phylogenetic data. Types of trees include:

1)

An evolutionary tree can be constructed based on the two major principles called maximum parsimony and maximum likelihood. The maximum parsimony is a simple and an intuitive criterion in which a phylogenetic tree constructed with an optimality criterion and by reducing amount of homoplasy. The maximum likelihood is an advanced algorithm in which the phylogenetic tree is constructed based on the maximally occurrence of a parameter. Both these methods are widely used for tree construction, because they are simple and easy methods for analysis.

2)

The trees are helpful, because they can simple explain, which organism is evolved from which organism. We can know what type of the newly evolved characters that defines the generation of a new species. Very complex patterns of evolution can simply understood by phylogenetic trees.

3)

The genes, which are evolved from a common ancestral gene in different species, are called Orthologs genes. The gens, which duplicated form a genome itself, are called Paralogs genes. The Orthologs have same function in all most all species, but Paralogs have different functions. Analysis of this type of genes can be used as a key feature for construction of phylogenetic trees.

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