Hardy Weinberg Notes

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Hardy Weinberg Notes
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Allele Frequencies

• Allele frequencies the abundance of each kind
  of allele in a population
• To compare, use Hardy-Weinberg equilibrium (equati
  on p2 2pq q2 1)
• p2 frequency of homo dom
• 2pq frequency of hetero
• q2 frequency of homo recess
• p frequency of dominant allele
• q frequency of the recessive allele

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Hardy-Weinberg Theorem describes a
non-evolving population

• Must meet 5 conditions for no change in
  frequencies of alleles at a given gene locus
• 1. No gene mutations have occurred.
• 2. Population is very large.
• 3. Population is isolated from other pops of
  the species (no immigration or
  emigration.)
• 4. No natural selection
• 5. Mating is random.

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Hardy-Weinberg example

• The allele for the ability to roll ones tongue
  is dominant (R) over the allele for the lack of
  this ability (r).
• In a population of 500 individuals, 25 show the
  recessive phenotype. How many individuals would
  you expect to be homo dom and heterozy?

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• The equation p2 2pq q2 1
• Therefore, p q 1
• 500 organisms, 25 are rr thus q2 .25
• so 125 organisms are rr
• If q2 .25, the q.5
• Thus, p .5 1, leaves p .5
• So, p2 .25, so 125 organisms are RR
• 2pq leaves the heterozygotes, so
• 2(.5)(.5) .5 or 50, so 250 organisms are Rr

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Practice Problem

• Seventy percent of a population show the
  dominant trait while 30 are recessive. What
  percentage of the population are carriers
  (heterozygous for dominant trait)?