11. How do we use the principles of max parsimony and max likelihood to construc
ID: 72083 • Letter: 1
Question
11. How do we use the principles of max parsimony and max likelihood to construct trees? How
do they lend support to our trees?
12. Why are trees helpful?
13. 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?
14. 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?
15. 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
11.
Max parsimony is an intuitive and simple criterion used to construct phylogeny trees. It is easy to score a phylogenetic tree by counting the number of character-state changes. Maximum-likelihood estimation is a statistical method of estimating the parameters of a statistical model. In max likelihood method, a set of model parameters that maximize the likelihood function are selected. This eventually maximizes the agreement of selected model with the observed data.
12.
Trees are useful in many different ways. ThJey are useful to solve scientific and practical problems. It helps us to understand the evolutionary relationships between different sets of organisms. They are of great use in bioinformatics.
13.
Orthologous genes are homologous genes that diverged after a speciation event, while paralogous genes are homologous genes that occur within one species and have diverged after a duplication event. Paralogous genes arise during gene duplication. The genes that produce hemoglobin and myoglobin proteins have both orthologous and paralogous relationships.
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