slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
How does migration cause change in allele frequencies? PowerPoint Presentation
Download Presentation
How does migration cause change in allele frequencies?

Loading in 2 Seconds...

play fullscreen
1 / 15

How does migration cause change in allele frequencies? - PowerPoint PPT Presentation


  • 336 Views
  • Uploaded on

How does migration cause change in allele frequencies?. Population 1 (“island”) 950 AA 0 A a 0 aa. Population 2 (“mainland”) 0% AA 0% A a 100% aa. “fixed”. “fixed”. 50 aa. Allele freq. before migration:. Did allele frequencies change?. Allele freq. after migration:.

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 'How does migration cause change in allele frequencies?' - Jims


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
slide1

Howdoes migration cause change in allele frequencies?

Population 1 (“island”)

950 AA

0Aa

0 aa

Population 2 (“mainland”)

0% AA

0%Aa

100% aa

“fixed”

“fixed”

50 aa

Allele freq. before migration:

Did allele frequencies change?

Allele freq. after migration:

Is the population in

Hardy-Weinberg equilibrium?

p2 = (0.95)2 = 0.9025

2pq = 2(0.95)(0.05) = 0.0950

q2 = (0.05)2 = 0.0025

What if migration continued

over many generations?

slide2

Migrationmakes population more similar

AlleleA1 simulation – one-way migration (gene flow)

Population 1 (“island”)

Population 2 (“mainland”)

A

a

a

A

A

a

a

A

A

a

a

A

a

A

a

A

a

A

a

a

a

a

a

A

A

a

A

a

A

a

A

A

a

a

a

a

a

A

A

a

a

a

A

A

a

A

A

a

a

a

A

a

A

a

A

a

a

a

slide3

Migrationmakes population more similar

AlleleA1 simulation – one-way migration (gene flow)

Population 1 (“island”)

Population 2 (“mainland”)

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

Real life – gene flow can be one-way or two-way

Population 1

Population 2

a

a

A

A

a

a

A

a

A

a

A

a

A

A

a

A

a

A

a

a

a

A

a

a

A

A

a

A

a

A

a

a

A

A

a

a

a

a

a

A

A

a

A

A

A

A

a

a

a

a

A

A

a

a

a

A

a

slide4

Migrationmakes population more similar

AlleleA1 simulation – one-way migration (gene flow)

Population 1 (“island”)

Population 2 (“mainland”)

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

Real life – gene flow can be one-way or two-way

Population 1

Population 2

A

A

A

A

a

A

a

a

a

a

a

a

a

A

A

a

a

A

A

A

A

a

A

a

a

A

A

a

a

A

a

A

a

a

a

A

a

A

A

A

A

a

A

A

A

a

a

A

A

A

a

a

a

what can change population genetic structure

introduces new alleles

diversity within populations

introduces new alleles

diversity within populations

diversity between populations

loss of alleles

diversity within populations

diversity between populations

removes harmful alleles

usually diversity within populations

can or diversity between populations

What can change population genetic structure?
  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating

change in

p & q

genotype

freq’s aren’t

p2, 2pq, q2

slide6

introduces new alleles

diversity within populations

removes harmful alleles

usually diversity within populations

can or diversity between populations

Population genetic forcescan interact

  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating
slide7

introduces new alleles

diversity within populations

removes harmful alleles

diversity within populations

Population genetic forcescan interact

mutation vs. selection

Mutation-selection balance

recurrent mutations offset removal by selection

more mutations

per generation

 higher frequency of mutant allele at equilibrium

stronger selection

against mutant allele

 lower frequency of mutant allele at equilibrium

slide8

introduces new alleles

diversity within populations

diversity between populations

removes harmful alleles

usually diversity within populations

can or diversity between populations

Population genetic forcescan interact

  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating
slide9

removes harmful alleles

usually diversity within populations

can or diversity between populations

introduces new alleles

diversity within populations

diversity between populations

Population genetic forcescan interact

migration vs. selection

Balance between migration and selection

-input from migration offsets removal by selection

- homogenizing force of migration offset by diversifying force of selection

more migration

per generation

higher frequency of migrant allele at equilibrium;

populations become similar

stronger selection

against migrant allele

lower frequency of migrant allele at equilibrium;

populations remain distinct

slide10

introduces new alleles

diversity within populations

diversity between populations

loss of alleles

diversity within populations

diversity between populations

Population genetic forcescan interact

  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating
slide11

introduces new alleles

diversity within populations

diversity between populations

loss of alleles

diversity within populations

diversity between populations

Population genetic forcescan interact

migration vs. drift

Balance between migration and drift

- input from migration offsets removal by drift

- homogenizing force of migration offset by diversifying force of drift

more migration

per generation

higher frequency of migrant allele at equilibrium;

populations become similar

smaller

population size

drift affects frequency of migrant allele (usually lost);

populations remain distinct

Balance depends on population size

slide12

loss of alleles

diversity within populations

diversity between populations

removes harmful alleles

usually diversity within populations

can or diversity between populations

Population genetic forcescan interact

  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating
slide13

removes harmful alleles

diversity within populations

can or diversity between populations

loss of alleles

diversity within populations

diversity between populations

Population genetic forcescan interact

selection vs. drift

Balance between selection and drift

- random force of drift can oppose selection against deleterious allele

- drift opposes adaptation

stronger selection

against deleterious allele

lower frequency of deleterious allele at equilibrium;

populations become adapted

smaller

population size

drift affects frequency of deleterious allele (may be kept);

populations drift

Balance depends on population size

what can change population genetic structure1
What can change population genetic structure?
  • mutation
  • migration
  • genetic drift
  • selection
  • non-random mating

change in

p & q

genotype

freq’s aren’t

p2, 2pq, q2

slide15

Non-random matingcan change population genetic structure

Non-random mating

– does not change allele frequencies

– does cause genotype frequencies to differ from p2, 2pq, q2

Types of non-random mating

Assortative mating – mates are genetically similar

ex: inbreeding – mating between close relatives

includes self-pollination

Disassortative mating – mates are genetically different