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Evolutionary and Population Genetics
Lecture 1 – 14/1/14
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appreciate that population genetic principles can be applied to many biological
disciplines
know the four main processes affecting allele frequencies
recall basic Mendelian inheritance

What is Population Genetics?
=The mechanism of evolution
 A link between population biology and genetics
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Need to
look at variation and need to understand finger00 print profilingprobability of matching that and actually getting correct result
o Breeding of domestic plants and animals

Human History
Questions
What’s this figure showing?

Picture based on molecular markers- colours show different allele combinations
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Disease distribution

This is a map showing areas of malaria common areas before control programmes
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Other map shows how then
those areas have sickle cell anaemia problems
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All
recovered from it, but makes the populations very genetically uniform
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When population recovered100000+ organisms, still has issues with it
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How do you study population genetics?
Historically Theory rich and data poor subject
Now Data rich due to much more powerful molecular methods
 Theory needed to make sense of the data
Questions
Whats a population bottleneck?
How do you study population genetics? In the past? Future?

Evolutionary processes
 A reminder: evolution = a change of allele frequencies
 What are they?
 Which processes increase meiosis, recombination, independent
assortment, genetic mutations, immigration
 Which decrease genetic variation? Selection
 Are they random or not? Recombination- recombines but doesn’t actually
change frequency, just recombines them
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Immigrationacross the world doesn’t introduce new alleles, but for the specific location
only
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Purely random process

Selection
• Directional process
• Acts on fitness differences of genotypes - requires phenotypic variation with a
genetic basis
• Adaptation
• Usually reduces genetic variation- disruptive selection increases genetic
variation
Gene flow
• Structure of populations (spatial or ecological)
• Migration: Reduces divergence between populations
• Can restore some genetic variability

All of these processes act together in the real world!
Questions
Whats processes effect evolution? How?

Mendelian genetics – a reminder
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Mendelian inheritance is the basis for population genetics
Mendel did experiments on peas

Terminology
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Phenotype: a visible or measurable trait or set of traits
Genotype: the combination of alleles at a genetic locus or a set of loci in an
individual
Genetic locus: a stretch of DNA in the genome
Gene: a stretch of DNA coding for a protein or functional RNA
Allele: a variant of a gene or more generally a genetic locus

Mendel’s first law: segregation

¾ of F2: yellow seeds

¼

F2

F3

½

¼ of F2: green seeds

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Individuals have a pair of alleles for a given trait and these segregate
separately into gametes
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More terminology
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DominantAn allele is dominant when the associated phenotype is
expressed in the homozygous and heterozygous state
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Co-dominant Alleles are codominant when the heterozygotes have an
intermediate
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Genotype: the combination of
alleles at a genetic locus or a set of loci in an individual

Summary
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A very quick overview of population genetics:
Population genetic principles are widely applicable
Four main evolutionary processes:
o Mutation
o Genetic Drift
o Selection
o Gene Flow
Laws of inheritance essential for our understanding



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