The Founder Effect and Genetic Bottlenecks

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The Founder Effect and Genetic Bottlenecks
Learning objective To understand how the
founder effect and genetic bottlenecks influence
genetic diversity.
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Learning Objective To understand how the
founder effect and genetic bottlenecks influence
genetic diversity.

• Learning Outcomes
• Good.....if you can model the founder effect and
  genetic bottlenecks.
• Better......if you can interpret the results of
  the model in terms of the effect on genetic
  diversity.
• Exceptional......if you can synthesise
  information on genetic diversity with your own
  understanding.

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Question What is genetic diversity?
Answer The variability within a species due to
differences in alleles.
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Starter

• Hold up your arrow to state whether there will be
  an increase or decrease in genetic diversity
  if.......
• There is an increase in the variety of alleles in
  a population.
• Closely related cats are bred to develop
  varieties with long hair.
• Seeds from a plant community on Iceland reach a
  new volcanic island and establish a community.
• There is a mutation of an allele in a population.

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• Two factors that influence genetic diversity are
• The founder effect
• Genetic bottlenecks

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Modelling the founder effect and genetic
bottlenecks.........
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The Founder Effect

• Occurs when a few individuals from a population
  colonise a new region.
• Only a small fraction of the alleles are carried
  with them.
• The new population that develops will show less
  genetic diversity than the original population.
• E.g. The Amish Population.

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Genetic Bottlenecks

• Populations may suffer a dramatic drop in
  numbers.
• This could be due to a chance event, such as a
  volcanic eruption, earthquake, flood, fires etc
• The few survivors will contain a much smaller
  variety of alleles than the original population.
• The genetic diversity of the new population will
  remain restricted.
• E.g. Cheetahs

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• Unit 2 June 2009 Exam Question
• 5 Marks

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• Answers
• Mark your partners work according to the mark
  scheme below.
• You must include a total (out of 5).
• You must write a comment on how they could
  improve.

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Examiners Report Although knowledge of genetic
bottlenecks was generally sound, relatively few
candidates were able to explain how the founder
effect might have influenced the genetic
diversity of seals after 1910. Answers to part
(ii) frequently involved a rewrite of the
response to part.
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Learning Objective To understand how the
founder effect and genetic bottlenecks influence
genetic diversity.

• Learning Outcomes
• Good.....if you can model the founder effect and
  genetic bottlenecks.
• Better......if you can interpret the results of
  the model in terms of the effect on genetic
  diversity.
• Exceptional......if you can synthesise
  information on genetic diversity with your own
  understanding.