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Measuring genetic diversity in natural populations

Measuring genetic diversity in natural populations. Protein electrophoresis, or allozyme electrophoresis: the earliest widely-used method for screening population genetic diversity. Heterozygotes Heterozygosity (H) = 8/20 = 0.40. *. *. *. *. *. *. *. *. Allozyme Electrophoresis:

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Measuring genetic diversity in natural populations

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  1. Measuring genetic diversity in natural populations

  2. Protein electrophoresis, or allozyme electrophoresis: the earliest widely-used method for screening population genetic diversity

  3. Heterozygotes • Heterozygosity (H) = 8/20 = 0.40 * * * * * * * * • Allozyme Electrophoresis: • Each enzyme protein (this is phosphoglucomutase) is the product of a single genetic locus • Different genetic forms of the enzyme at this locus appear as bands on the gel; these are called allozymes • Allozymes are inherited as Mendelian codominant alleles at each locus

  4. DNA fragments that are used to detect variation are also separated and analyzed using gel electrophoresis. This gel shows the DNA fragments from an assay for Restriction Fragment Length Polymorphism (RFLP). RFLPs, like all DNA-based assays for genetic variation, reveal much more diversity than seen when screening allozymes.

  5. This gel shows three possible genotypes at the CCR5 coreceptor locus DNA fragments from this locus are produced by PCR amplification, followed by restriction enzyme digestion

  6. Restriction enzyme digestion of the “wild type” allele (no deletion) produces a 403 bp and a 332 bp fragment The 32 allele contains a 32 bp deletion, transforming the 403 to a 371 bp fragment

  7. Calculating allele frequencies at the CCR5 locus

  8. Patterns of genetic diversity clinal variation

  9. from Volpe and Rosenbaum (2000), p. 110

  10. Allozyme variation at the alcohol dehydrogenase (Adh) locus in D. melanogaster Nearly all populations are polymorphic for the slow AdhS andfast AdhFalleles In Australia (and 2 other continents) the locus shows a cline—increase in frequency of AdhStowards the equator

  11. The mummichog Fundulus heteroclitus shows clinal variation at lactate dehydrogenase-B: Ldh-Bb increases towards the north This allozyme has a higher catalytic efficiency at lower temperatures

  12. Allozyme surveys show that variation is nearly universal in humans and natural populations of animals and plants The average individual is heterozygous at 4-15% of its allozyme loci

  13. DNA sequence surveys reveal even more genetic variation

  14. In 15,000 cystic fibrosis patients (homozygous at CFTR): 30,000 different chromosomes 500 loss-of-function alleles

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