1. Molecular and Genomic Evolution Getting at the Gene Pool

2. Figure 26.1

3. What is Molecular Evolution? a change in nucleotide &/or amino acid sequences over time –molecular phylogenetics reconstructs lineages based on molecular differences

4. Determining and Comparing Sequences PCR (Polymerase Chain Reaction) –rapid amplification of DNA from many samples automated sequencing methods –rapid determination of sequences from PCR

5. Sequence Alignment Figure 26.2

6. Determining and Comparing Sequences homologous DNA sequences are compared by alignment –sequences of closely related groups have fewer differences

7. Determining and Comparing Sequences sequence changes accumulate at different rates in different parts of the genome –regions that encode functional products change relatively slowly synonymous changes are most common –non-coding regions may change rapidly

8. Figure 26.3

9. Determining and Comparing Sequences good historical evidence combined with good molecular evidence give the rate of change of a sequence some polypeptides have relatively constant amino acid substitution rates over time

10. Determining and Comparing Sequences a sequence with a constant rate of change can be used as a “molecular clock” –cytochrome c is in the electron transport chain in the mitochondrion of all eukaryotes

11. Figure 26.4

12. amino acid substitution rate of cytochrome c Figure 26.5

13. The Origin of New Protein Functions protein function can change –lysozyme, an antibacterial enzyme, is found in most animals. tears, saliva, milk, egg whites –some mammals use lysozyme in foregut fermentation, a type of digestion ruminants langurs

14. Langurs Figure 26.6

15. The Origin of New Protein Functions protein function can change –foregut fermentation arose in langurs and ruminants separately each descended from non-fermenting recent ancestors –langur and ruminant lysozymes share changes that protect them from digestion

16. Table 26.1

17. The Origin of New Protein Functions protein function can change –langur and ruminant lysozymes share changes that protect them from digestion –the hoazin, a foregut fermenting bird, makes a lysozyme with similar changes Figure 26.6

18. The Origin of New Protein Functions protein function can change –hoazin, langurs, ruminants all share distinctive amino acid substitutions in the same enzyme –therefore… they shared a recent common ancestor? homoplasy, such as convergent evolution, is identified by comparison with patterns of homology.

19. The Origin of New Genes Gene duplication yields new genes –duplicate genes may change together rRNA gene tandem arrays share changes so that members retain the same sequence –duplicate genes often change independently one copy of the gene is required to produce a normal product a duplicate copy may change its function by mutation

20. The Origin of New Genes Gene duplication yields new genes –duplicate genes are homologs paralogs are homologs in the same genome orthologs are homologs in different genomes –duplication of genes, chromosomes, or entire genomes can occur

21. The Origin of New Protein Functions duplicated proteins can change without harm to the organism –myoglobin,  -globin and  -globin gene families arose following gene duplication each family experienced later duplications

22. Figure 26.9

23. Figure 26.7

24. C-value Inflation Figure 26.8

25. A Relevant Mystery The C-value paradox –more-complex organisms have more DNA per genome than less-complex organisms –more-complex organisms have more genes than less-complex organisms –more-complex organisms have much higher proportions of non-coding DNA –the non-coding DNA has no known function

26. Molecular Phylogenetics different molecules change at different rates over time –rapidly changing molecules useful for recently diverged groups slow changing molecules for groups that diverged long ago

27. Molecular Phylogenetics different molecules change sequences at different rates over time –the gene for the small ribosomal RNA subunit changes very slowly –serves as one of the bases for the three domain classification of life

28. Figure 26.10 Molecular phylogenetics reconstructs the history of gene evolution

29. Molecular Phylogenetics The Big Bird story –Moas large flightless birds extinct for ~1000 years shared New Zealand with kiwis presumed to share a more recent common ancestor with kiwis than with other large flightless birds on other continents