The Founder Effect and Genetic
Bottlenecks
Learning objective:
To understand how the founder effect and
genetic bottlenecks influence genetic
diversity.
Learning Objective:
To understand how the founder effect and genetic
bottlenecks influence genetic diversity.
Learning Outcomes:
1. Good.....if you can model the founder effect and
genetic bottlenecks.
1. Better......if you can interpret the results of the model
in terms of the effect on genetic diversity.
1. Exceptional......if you can synthesise information on
genetic diversity with your own understanding.
Question: What is genetic diversity?
Answer: The variability within a
species due to differences in alleles.
Starter
• Hold up your arrow to state whether there will be an
increase or decrease in genetic diversity if.......
1. There is an increase in the variety of alleles in a
population.
1. Closely related cats are bred to develop varieties with
long hair.
1. Seeds from a plant community on Iceland reach a new
volcanic island and establish a community.
1. There is a mutation of an allele in a population.
• Two factors that influence
genetic diversity are:
1.The founder effect
1.Genetic bottlenecks
Modelling the founder
effect and genetic
bottlenecks.........
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.
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
•Unit 2 June 2009 –
Exam Question
5 Marks
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.
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.’
Learning Objective:
To understand how the founder effect and genetic
bottlenecks influence genetic diversity.
Learning Outcomes:
1. Good.....if you can model the founder effect and
genetic bottlenecks.
1. Better......if you can interpret the results of the model
in terms of the effect on genetic diversity.
1. Exceptional......if you can synthesise information on
genetic diversity with your own understanding.