Title: Measuring genetic diversity in natural populations
1Measuring genetic diversity in natural populations
2Protein 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
4DNA 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.
5This 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
6Restriction 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
7Calculating allele frequencies at the CCR5 locus
8(No Transcript)
9Patterns of genetic diversity
10from Volpe and Rosenbaum (2000), p. 110
11Allozyme variation at the alcohol dehydrogenase
(Adh) locus in D. melanogaster Nearly all
populations are polymorphic for the slow AdhS and
fast AdhF alleles In Australia (and 2 other
continents) the locus shows a clineincrease in
frequency of AdhS towards the equator
12The 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
13Allozyme 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
14DNA sequence surveys reveal even more genetic
variation
15In 15,000 cystic fibrosis patients (homozygous at
CFTR) 30,000 different chromosomes 500
loss-of-function alleles