Bio 321 F13 lecture 6 for post

gene1c varia1on required for evolu1onary

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Unformatted text preview: selection variation within populations very low high variation between populations much greater than intrapopulation variation not much greater than intra-population variation selection usually “purifying” “balancing” (heterozygot e advantage) h)p://www.monmsci.net/~kbaldwin/popgen.03.notes.pdf BIO 367/BEE 567 lecture 1 19 Evidence favors the Balance view (somewhat) •  Lewon1n, Hubby 1966 –  Used protein electrophoresis to show that varia1on at the molecular level was common •  Late 60s, 70s, 80s “era of allozymes” –  30- 50% of loci studied have at least 2 electrophore1c variant in popula1ons –  Individuals heterozygous at 6- 12% of loci •  (Drosophila) •  (human/mammals est. 6- 7%, based on amino acid sequences) BIO 367/BEE 567 lecture 1 20 Allozymes •  =“allele” + “enzyme” •  Polymorphisms involving charge differences in metabolic enzymes •  Recognized using electrophore1c separa1on of protein extracts •  Lewon1n and Hubby (1966) –  Examined 18 gene loci from 6 popula1ons (Drosophila pseudoobscura) –  Only 11 of 18 loci were monomorphic (no allozyme varia1on) –  39% of loci turned out to be polymorphic for allozymes –  Led to predic1on: 8- 15% of all loci will be polymorphic (typically expressed as likelihood an individual will be BIO367/BEE 567 Lab 1 Fall 05 heterozygous) http://en2.wikipedia.org/wiki/Amino_acid BIO367/BEE 567 Lab 1 Fall 05 =usually negative at physiological pH =usually positive at physiological pH =sometimes positive at physiological pH Amino acid subs1tu1ons •  May or may not change the charge of the protein •  If net charge of protein is altered, electrophore1c mobility will change –  Basis of “allozymes” (allele + enzyme) BIO367/BEE 567 Lab 1 Fall 05 BIO367/BEE 567 Lab 1 Fall 05 Allozymes are co-dominant markers =can tell all three genotypes previous slide only had homozygotes (inbred lines) example of heterozygotes for an allozome locus http://www.zoology.siu.edu/ heist/images/ SunfishAllozyme.jpg Taq polymerase Restric+on Endonucleases •  Also called “restric1on enzymes” •  Originally from bacteria –  What might bacteria use them for? •  Enzymes that cut DNA at precise sequences –  Dozens of different enzymes with different “cut sites” Restric1on cut sites are ouen variable: RFLPs = Restric1on Fragment Length Polymorphisms •  pre- PCR •  PCR- era isolate genomic DNA from in...
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