Genetic drift and mutation

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Drift
- Random change in allele frequencies from generation to
- generation due to sampling error
- Two main consequences:
- 1. Allele frequencies will change
- 2. Genetic variation will be lost
- Stronger in smaller populations
Reproduction as Poisson process
- • Probability of a given # of events happening in a period
- of time if each event happens independently and with
- a fixed probability of occurrence
- • Probability of k copies in generation 1:
Probability of survival
- • One allele will eventually drift to fixation...
- • Assume neutrality
- • Probability of it being the red one
- = q0 = 1/2N
Founder Effect
- • Change in allele frequencies when a new population
- arises from only a few individuals (the “founders”)
- • E.g. only a few fish make it to an island
- • E.g. only a few individuals are introduced to a new
- habitat
N

= census population (total)
Ne
- = breeding population
- • Factors that affect Ne
- – Unequal sex ratios
- – High variance in reproduc+ve success
- – Changes in population size
- – Overlapping generations
- • Long term average number of successfully
- breeding individuals
- • Less than the census size
Assumptions
- • Equal sex ratio
- • All individuals have an equal chance at
- reproducing
- • Constant population size
- • Non-overlapping (discrete) generations
Effect of variation
- • High levels of variation =
- low ratio of Ne / N
Study formation
Effect of population fluctuations
- • Years with small populations =
- low ratio of Ne / N
- • Current population may be large, but
- effective size could be small
Marine species
Know the three types of survivorship

Author

doncheto

307807

Card Set

Genetic drift and mutation

Description

asd

Updated

2015-09-14T17:51:26Z

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