Evolution of mankind.
   Analysis of mitochondrial DNA proposes that Homo sapiens 
     evolved from one group of Homo erectus in Africa (African 
     Eve) 100,000 – 200,000 years ago.
                                       American indians I, 
           Europeans                   25-35,000
           40-50,000                          American indians II, 
                                                   7-9,000
                                       Asians
                                       55-75,000
                             Africans
                             100,000
        Adam appeared 250,000 years ago, much earlier!
                                   
             Mechanisms of evolution.
    - Evolution is caused by mutations of genes.
    - Mutations spread through the population via 
       genetic drift and/or natural selection.
    - If mutant gene produces an advantage (new 
       morphological character), this feature will be 
       inherited by all descendant species.
                                 
      Mutational changes of DNA sequences.
         1. Substitution.                         3. Insertion.
       Thr     Tyr   Leu   Leu              Thr    Tyr   Leu   Leu
       ACC  TAT  TTG  CTG            ACC  TAT  TTG  CTG
               
       ACC  TCT  TTG  CTG            ACC  TAC  TTT  GCT G—
       Thr     Tyr   Leu   Leu              Thr    Tyr    Phe   Ala 
       2. Deletion.                              4. Inversion.
      Thr    Tyr    Leu   Leu              Thr    Tyr    Leu   Leu
      ACC  TAT   TTG  CTG           ACC  TAT  TTG  CTG 
      ACC  TAT   TGC  TG-            ACC  TTT   ATG  CTG
      Thr    Tyr    Cys                       Thr    Phe   Met   Leu
                                   
        Gene duplication and recombination.
 New genes/proteins occur through the gene duplication and 
    recombination.
          Ancestral globin                  Gene 1
                  duplication                  +
                                            Gene 2
        globin        globin
      hemoglobin    myoglobin
                                            New gene
           Duplication                  Recombination
                                  
                       Codon usage.
     Phe UUU    Ser UCU   Tyr UAU
         UUC        UCC       UAC
     Leu UUA        UCA   Cys UGU
         UUG        UCG       UGC
     Frequencies of different codons for the same amino acid are 
       different. Codon usage bias is caused:
     - Translationary machinery tends to use abundant tRNA 
       (and codons corresponding to these tRNA). Codon usage 
       bias is the same for all highly expressed genes in the 
       same organism.
     - Mutation pressure. Difference between mutation rates 
       between GC  AT and AT  GC. GC-content is different 
       in different organisms.