Survey of softwares for phylogenetic analysis
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Survey of softwares for phylogenetic analysis
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Survey of softwares for phylogenetic analysis
- 1. Survey of softwares for phylogenetic analysis ag1805xag1805x
- 2. PhylogeneticsPhylogenetics Phylogenetics - in biology – is the study of the evolutionary history and relationships among individuals or groups of organisms (e.g. species, or populations). These relationships are discovered through phylogenetic inference methods that evaluate observed heritable traits, such as DNA sequences or morphology under a model of evolution of these traits. The result of these analyses is a phylogeny (also known as a phylogenetic tree) – a hypothesis about the history of evolutionary relationships
- 3. Phylogenetic treePhylogenetic tree Phylogenetic tree also known as “evolutionary tree” is the graphical representation of the evolutionary relationship between the taxa/genes in question. A dendrogram is a broad term for the diagrammatic representation of a phylogenetic tree.
- 4. The cladogram is a dendogram which explains only genealogy of the taxa but says nothing about the branch lengths or time periods of divergence.
- 5. The phylogram (additive tree) is a phylogenetic tree that explicitly represents a number of character changes (nucleotide/amino acid changes/number of character variations) through its branch lengths. In case of phylogram the evolutionary distance between any two taxa is given by sum of the branch lengths connected them. Though these trees may be rooted or unrooted, often these trees lack a root.
- 6. A chronogram (ultra metric) is a rooted phylogenetic tree that possesses all the characteristics of an additive tree, in addition with the assumption of molecular clock determination of the molecular divergence time between taxa can be possible. The molecular clock hypothesis assumes that every site in a protein or coding nucleotide sequence from all the species evolve at a constant rate. Furthermore, the chronogram consists of taxa placed equidistant from the ancestor which cannot be seen in case of phylogram.
- 7. Phenetics (taximetrics) infers the relationship between the taxa that usually involves morphology or other observable traits as phylogenetic informative markers.
- 8. A tree that shows the evolution of the genes is known as gene tree. While, tree that shows the evolution of species is known as species' tree
- 9. The whole process of construction of the phylogenetic tree is divided into five different steps, viz. Step 1: Choosing an appropriate markers for the phylogenetic analysis Step 2: Multiple sequence alignments Step 3: Selection of an evolutionary model Step 4: Phylogenetic reconstruction Step 5: Evaluation of the phylogenetic tree Process of construction of the phylogenetic treeProcess of construction of the phylogenetic tree
- 10. Step 1: Choosing an appropriate markers for theStep 1: Choosing an appropriate markers for the phylogenetic analysisphylogenetic analysis Any biological information that can be used to infer the evolutionary relationship among the taxa is known as a phylogenetic information marker. It can be anything like DNA, RNA, protein, RFLP, AFLP, ISSR, allozymes, and conserved intronic positions, etc. Identification of conserved genetic loci (coding- or non- coding) is the first step in analyzing the phylogenetic relationship. Both coding (genes) and non-coding genetic region can be used for the analysis of phylogenetic relationships.
- 11. However, selected sequence(s) must satisfy the defined necessary rules: (a) the sequence should have a long evolutionary history of conservation, as this feature facilitates, firstly in the preservation of long evolution-selection episodes, and secondly, aids in easy amplification of the target sequences from distant taxa. (b) conserved, slow evolving genes may be used to resolve the evolutionary relationship between distantly related species while fast evolving genes should be choose for the recently evolved species or intra-species. (c) amino acid sequences are more informative while inferring the evolutionary relationship among distantly related taxa, and conversely, nucleotide information for recently evolved/closely related species.
- 12. (d) the sequences need to be employed in the phylogenetic analysis should be tested for their usability in a given lineage (for instance, mitochondrial (cytochrome C oxidase subunit I & II (CoxI & II)), chloroplast (trnH-psbA, matK, rpoC, rpoB, rbcL), and nuclear (16S ribosomal RNA) conserved genes are preferred to use for analyzing animal, plant, and microbial species, respectively-and are called “barcode genes”). (e) finally, if, objective is to estimate the divergence periods between taxa, the selected gene or protein sequences should essentially follow the molecular clock hypothesis. However, recently relaxed molecular clock models have also been proposed. This step follows successful polymerase chain reaction amplification of the target gene/protein, followed by sequencing and editing of the sequences for further analysis.
- 13. Step 2: Multiple sequence alignmentsStep 2: Multiple sequence alignments ●The main aim of multiple sequence alignment is to compare the three or more nucleotide or protein sequences and to provide the basis for calculation of the sequence diversities/divergences to infer the evolutionary relationship among the taxa. ●Different models (discussed below) have been proposed based on various assumptions to calculate the sequence divergences between the sequences or taxa. Hence, the correct sequence alignment is mandatory in order to get the true phylogeny that is representative of the evolutionary relationship among the taxa.
- 14. Step 3: Selection of an evolutionary modelStep 3: Selection of an evolutionary model Evolutionary models are sets of assumptions about the process of nucleotide or aminoacid substitution. They describe the different probabilities of change from one nucleotide or amino acid to another, with the aim of correcting for unseen changes along the Phylogeny.
- 15. Step 4: Phylogenetic reconstructionStep 4: Phylogenetic reconstruction Two different methodologies are employed by the presently available programs to generate the dendograms; (a) clustering methods-where two most closely related taxa are placed under single inter-node and further add third taxa considering within internodes taxa as a single group. In this way, the program progressively adds the other remaining taxa to yield final phylogenetic tree (b) second type of methods generate the 'n' number of trees proportional to the number of taxa involved in the phylogenetic analysis followed by the selection of best fit tree topology (increased likelihood or probability) for a given evolutionary model.
- 16. Step 5: Evaluating the phylogenetic treeStep 5: Evaluating the phylogenetic tree This process can be performed using two evaluation methods, namely bootstrap method and interior-branch test.
- 18. Phylogenetic information marker: Cytochrome C oxidase subunit I (CoxI) Organisms: Homo sapiens (Human) Bos taurus (Bovine) Danio rerio (Zebrafish) Sus scrofa (Pig) Ovis aries (Sheep) Software used: Clustal Omega (MSA) & Clustal W2 phylogeny
- 19. Downloading the COX1 sequence from UniProt
- 25. Multiple Sequence Alignment using Clustal Omega
- 26. MSA result page
- 27. Phylogenetic tree construction using ClustalW2 Phylogeny
- 28. Result page of tree construction
- 34. Description: Fast and free multiplatform tree editor Methods: based Phylip 3.6 package algorithms
- 37. ag1805xag1805x