genetic drift n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Genetic Drift PowerPoint Presentation
Download Presentation
Genetic Drift

Loading in 2 Seconds...

play fullscreen
1 / 4

Genetic Drift - PowerPoint PPT Presentation


  • 274 Views
  • Uploaded on

Genetic Drift. Random change in allele frequency Just by chance or chance events (migrations, natural disasters, etc) Most effect on smaller populations (≤100) Founder effect- allele frequencies change as a result of migration of a small subgroup of a pop.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Genetic Drift' - gazelle


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
genetic drift
Genetic Drift
  • Random change in allele frequency
    • Just by chance or chance events (migrations, natural disasters, etc)
  • Most effect on smaller populations (≤100)
  • Founder effect- allele frequencies change as a result of migration of a small subgroup of a pop.
    • Chance events can reduce pop. size or create new, smaller pop.s from an original larger pop.
genetic equilibrium
Genetic equilibrium
  • Hardy-Weinberg principle- allele frequencies in a population will remain constant unless 1 or  factors causes those alleles to change
  • Genetic Equilibrium- allele frequencies in the pop. remain the same, nothing is changing
    • Conditions under which evolution will not occur
  • 5 Conditions
    • Random Mating
    • No Immigration or Emigration (Migration)
    • No Mutations
    • No Natural Selection
    • Large Populations
hardy weinberg equation
Hardy-Weinberg Equation
  • p2 + 2pq + q2 = 1
  • p + q = 1
    • p=frequency of dominant allele, q= frequency of recessive allele
    • p2 = frequency of individuals who are homozygous dominant, q2 = frequency of individuals who are homozygous recessive, 2pq= frequency of individuals who are heterozygous
  • If the frequency of people in the United States that have a certain recessive trait is 2% (or 0.02), what is the frequency of the allele for that trait?
    • q2 = frequency of individuals who are homozygous recessive = 0.02
    • q= frequency of recessive allele= √0.02 = 0.14 or 14%
sample problem
Sample Problem
  • A certain recessive disease has a frequency of 1 in 2500 people. What is the frequency of each allele and the frequency of carriers? (Assuming the population is at Hardy-Weinberg equilibrium)
    • What is the genotype of a recessive disease?
    • So q2= 1/2500= 0.0004, and q= √0.0004 = 0.02
    • If q is present 0.02 or 2% of the time, and p is the only other allele, how often is p present?
    • So q= 0.02, p= 0.98, those are the frequencies of the alleles!
    • What is the genotype of a carrier of a recessive disease?
  • p2 + 2pq + q2 = 1
    • So 2pq= 2 x 0.02 x 0.98= 0.04
    • Frequency of homozygous dominant= 0.982= 0.96
    • Frequency of homozygous recessive= 0.022= 0.0004
    • 0.96 + 0.04 + 0.0004= 1