How do we measure variation

How do we measure variation - the same rate in the gel. DNA...

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How do we measure variation? To show that there is a genetic basis to a continuously varying character one can study 1) resemblance among relatives : look at the offspring of individuals from parents in different parts of the distribution; can estimate heritability (more later). 2) artificial selection : pigeons and dogs show that there is variation present; does not tell how much variation Protein electrophoresis : phenotype = gene product of specific locus (loci). Took off in mid 60's (Lewontin and Hubby, 1966; Harris, 1966); still used. Grind up organism in buffer, apply homogenate to gel (starch, acrylamide), apply electric field, proteins migrate in gel according to charge, stain gel with histochemical stain for enzyme activity, bands reveal variation. Do this for many loci and can estimate: proportion of loci polymorphic per population (10-60%, depending on organism); proportion of loci heterozygous per individual (3-20% depending on organism). The technique provides a minimum estimate because different amino acid sequences may migrate at
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Unformatted text preview: the same rate in the gel. DNA variation. Measure the genetic material directly; sequencing is the most precise but the most laborious; restriction enzyme analysis faster but has less information. These techniques have revealed that there is even more genetic variation that what was revealed by protein electrophoresis. Hence the debate between the Classical and Balance schools of genetic variation has evolved into a debate about the forces maintaining genetic variation: the Neutralist-Selectionist controversy (or debate). Some loci are neutral; others under selection (more in lecture on Molecular Evolution). The debate is not over. How is variation apportioned within and among populations? Hierarchy in patterns of variation: are populations either melanistic or normal; or do populations contain some of both; if so what are the frequencies in different populations? Is the variation within or among populations ? Spatial Patterns of Variation...
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This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

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