Lecture 4

Transcript

1. Genotype:  The  actual  gene-c   sequence(s)  that  an  individual  has     Phenotype:  The  expression  of   that  genotype     Hair  color  is  the  resul-ng  phenotype   of  a  specific  genotype.    
2. Varia.on:     •  offspring  are  not  exact  copies  of  their  parents   •  Individuals  in  a  popula-on  vary  from  one  another       Mechanisms  of  Varia.on:     •  Muta-on   •  Sexual  reproduc-on   •  Recombina-on    
3. All  cellular  life  has  a  shared   evolu-onary  history,  and   some  genes  are  shared  by  all   organisms.  
4. Tradi-onal  approaches  to  inferring   rela-onships  between  organisms  were   morphology-­‐based.  
6. Chicken              Tyrannosaurus  Rex         Human              Stegosaurus     What  is  the  rela.onship?  
8. Tradi-onal  approaches  to  inferring   rela-onships  between  organisms   were  morphology-­‐based.     Modern  approaches  tend  to  be   sequence  based:  (possibly)  less   subjec-ve,  cheaper,  and  more   data.  
9. ACCAGGTT The  random  accumula-on  of   muta%ons  (changes  to  gene   sequences  over  evolu-onary   -me)  gives  us  informa-on   for  iden-fying  and   comparing  organisms.   Time
10. ACCAGGTT ACCAGGTT ACCATGTT ACTAGGAT Time The  random  accumula-on  of   muta%ons  (changes  to  gene   sequences  over  evolu-onary   -me)  gives  us  informa-on   for  iden-fying  and   comparing  organisms.  
11. ACCAGGTT ACCAGGTT ACCATGTT ACTAGGAT TCCATGTT ACCATATT ACTAGCAT ACTAGTAT ACCAGGTT Time The  random  accumula-on  of   muta%ons  (changes  to  gene   sequences  over  evolu-onary   -me)  gives  us  informa-on   for  iden-fying  and   comparing  organisms.  
12. ACCAGGTT ACCAGGTT ACCATGTT ACTAGGAT TCCATGTT ACCATATT ACTAGCAT ACTAGTAT ACCAGGTT ACCATATT ACTAGCAT ACTAGTAT TCAATGTT TCCATGTT ACCAGGTT Time The  random  accumula-on  of   muta%ons  (changes  to  gene   sequences  over  evolu-onary   -me)  gives  us  informa-on   for  iden-fying  and   comparing  organisms.  
13. What  if  the  rela-onship  of  sequences  is  unknown?     TCAATGTT     TCCATGTT     ACCATATT     ACTAGCAT     ACTAGTAT         ACCATATT ACTAGCAT ACTAGTAT TCAATGTT TCCATGTT ACCAGGTT
14. Con-nues  for  six  pages…  
15. Figure 1-22 Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
16. Figure 1-21 Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
17. Table 1-2 Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
18. Fitness:    The  number  of  viable  offspring  produced     Selec-on:      Not  all  offspring  reproduce  equally      mechanism:      “survival  of  the  fiSest”  or  the  “Preserva-on  of   Favoured  Races  in  the  Struggle  for  Life”     muta-ons  are  always  random,  but  they  can   some-mes  result  in  an  adap-ve  change    
19. Natural  selec-on  isn’t  the  only   mechanism  for  changing  gene   frequencies  in  a  popula-on:  “gene-c   driX”  or  changes  in  frequencies  due  to   random  sampling  also  plays  a  role.  
20. Gene-c  boSleneck  example:      IPython  notebook  
21. Homologs,  paralogs,  and  orthologs  
22. Figure 1-25a Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
23. Figure 1-25b Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
24. Figure 1-25c Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
25. Figure 1-25 Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008) Homologs,  paralogs,  and  orthologs  
26. Figure 1-26 Molecular Biology of the Cell, Fifth Edition (© Garland Science 2008)
27. Are  all  muta-ons  equally  well  tolerated?    
28. Types  of  changes:      beneficial  (i.e.,  result  in  increased  fitness  of  the   organism):  rare,  but  likely  to  be  propagated        selec-vely  neutral:  may  or  may  not  be  propagated        deleterious  (i.e.,  result  in  decreased  fitness  of  the   organism):  unlikely  to  be  propagated  
29. Why  might  a  deleterious  muta-on   propagate  through-­‐out  a  popula-on?  
30. Why  might  a  deleterious  muta-on   propagate  through-­‐out  a  popula-on?   Red  blood  cells  assume   an  abnormal,  rigid  shape   and  exhibit  reduced   flexibility.       These  sickle-­‐shaped  cells   build  up  in  veins  and   capillaries,  and  obstruct   blood  flow  causing  pain   and  -ssue  damage.       hSp://www.nature.com/scitable/topicpage/sickle-­‐cell-­‐anemia-­‐a-­‐look-­‐at-­‐global-­‐8756219  
31. Sickle  trait:  one  in   three  individuals  in   sub-­‐Saharan  Africa;   one  in  five   thousand  in  USA.   hSp://www.nature.com/scitable/topicpage/sickle-­‐cell-­‐anemia-­‐a-­‐look-­‐at-­‐global-­‐8756219  
32. hSp://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/hbb.shtml   Glutamic  acid   Valine  
33. hSp://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/hbb.shtml  
34. hSp://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/hbb.shtml  
35. Why  might  a  deleterious  muta-on   propagate  through-­‐out  a  popula-on?   The  sickle  cell  trait  confers  malaria  resistance  (although  the  mechanism   isn’t  fully  understood),  so  more  individuals  with  the  trait  will  survive  to   reproduce  and  pass  on  the  mutant  gene.  
36. This  work  is  licensed  under  the  Crea-ve  Commons  ASribu-on  3.0  United  States  License.  To  view  a   copy  of  this  license,  visit   hSp://crea-vecommons.org/licenses/by/3.0/us/  or  send  a  leSer  to  Crea-ve  Commons,  171   Second  Street,  Suite  300,  San  Francisco,  California,  94105,  USA.     Feel  free  to  use  or  modify  these  slides,  but  please  credit  me  by  placing  the  following  aSribu-on   informa-on  where  you  feel  that  it  makes  sense:  Greg  Caporaso,  www.caporaso.us.