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5.4. The UPGMA algorithm

We know how to fill an array with the values of the distances between sequences, pairs of sequences which are available in the file. This array of distances will be the input of our algorithm for reconstructing phylogenetic trees. The name of this algorithm israther complicated but the method itself is rather simple,too simple indeed. We will see that. The name standsfor Unweighted Pair Group Method with Arithmetic Mean, wewill understand these terms along the presentationof the algorithm. The algorithm starts withan array of distances. Let's take this very simpleexample, it implies seven species and here we have the values of thedistances between these different sequences associated with a species. As you ...
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2.2. Genes: from Mendel to molecular biology

The notion of gene emerged withthe works of Gregor Mendel. Mendel studied the inheritance on some traits like the shape of pea plant seeds,through generations. He stated the famous laws of inheritance which, by the way, were rediscovered 50 years later. The important thing here tounderline is that these concepts of inheritance of genes and so on were very abstract. No physical supports ofthese genes were clarified. So, it's something which appearedlater through molecular biology. We now know that genes are thoseregions of DNA which code the information used by the cell to produce proteins. And, this is what Francis Crick stated as the central dogma of molecular biology. One gene ...
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2.9. Whole genome sequencing

Sequencing is anexponential technology. The progresses in this technologyallow now to a sequence whole genome, complete genome. What does it mean? Well let'stake two examples: some twenty years ago, to sequence the bacillus subtilis bacteria genome took something like ten years,thirty five laboratories and several millions of euros. It was partly a European project,now some hundreds of dollars and it can be done within a day. The human genome project, famoushuman genome project, more than ten years, three billiondollars, 19-91 dollars OK.Tomorrow certainly less than 1000 dollars per genome, it means that we can now sequence humangenomes, not one but many many human genomes for the sake ofcomparison, diagnosis and so ...
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4.1. How to predict gene/protein functions?

Last week we have seen that annotating a genome means first locating the genes on the DNA sequences that is the genes, the region coding for proteins. But this is indeed the first step,the next very important step is to be able to predict thefunctions of the genes. That is more correctly, the function of the protein coded by the genes. How can we predict thisgene or function protein? It is essentially based on thefact that we will retrieve genes or protein for which the sequenceis similar and for which we know the function. So we will seehow we can measure and compute the similarity between DNA or protein ...
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1.2. At the heart of the cell: the DNA macromolecule

During the last session, we saw how at the heart of the cell there's DNA in the nucleus, sometimes of cells, or directly in the cytoplasm of the bacteria. The DNA is what we call a macromolecule, that is a very long molecule. It's Avery, in 1944, who discovered that the DNA was the support of genetic information. But the scientists who are most well-known for DNA are Francis Crick and James Watson who discovered together, with Maurice Wilkins and Rosalind Franklin, in 1953, the structure of DNA, the famous double helix, the two strands. Here are Crick and Watson explaining on a very crude wire model far away ...
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