Models of sequence evolution

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Models of sequence evolution

• Chap. 4 Higgs and Attwood

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Nothing in biology makes sense except in the
light of evolution(T. Dobzhansky)

• Evolution at the molecular level means mutations
• Mutations in the genetic material that are passed
  to the progeny (offspring)
• Divergent and convergent evolution
• TERMINOLOGY
• Locus (gene)
• Alleles variants at a locus
• Polimorphisms number of alleles in a population
• Haploid(prokaryotic organisms)/Diploid
  (eukaryotic organisms)
• Diploids have two copies of each locus (paired
  chromosomes)
• Diploid individuals may be homozygous or
  eterozygous at a certain locus

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• TYPES OF MUTATIONS
• (A and G purines C and T/U are pyrimidines)
• Causes of mutations DNA damage, errors in the
  replication
• Transitions/ transversions

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Part of the alignment of the DNA sequencees of
the BRAC1 gene (fig.3.1)
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Alignment of the Brca1 protein sequences from the
same region of the gene as in fig. 3.1
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BASIC CONCEPTS UP TO THIS POINT HOMOLOGY,
ORTHOLOGY, PARALOGY
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Family tree of a gene over a population and its
generationstime is the background elusive
concept behind evolution
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The accumulation of substitutions in two
sequences descending from a common ancestor

• Q. Why evolutionary models?
• To infer d(A,B) from D(A,B)
• Through an evolutionary (probabilistic model)

Note D is not linear in time (see above) and is
not Additive
D12? D01D02