Individuals do not evolve populations evolve
Only natural selection leads to Adaptation
Modern evolutionary genetics
Early – macroscale
1960s – microscale
-Some genes with a very large effects
-Many with very small additive effects
Reverse transcription is possible
Primary transcript has no promoter –> mature transcript only exons –> proteins
Exon's code for proteins, tRNA, rRNA
Intron's, pseudogens, repetitive DNA
Purines include: A, G transition | C for G transversion
Pyrimidines include: C, T transition. | T for A transversion Lecture2
Transition– going from purine to purine or pyrimidine to pyrimidine.
Transversion– going from purine to pyrimidine or pyrimidine to purine.
-Transversions are much more difficult to do than transitions
- PURe As Gold -> purines = adenine and guanine
Measuring genetic variation
- What is evolutionarygenetics?
Interface between ecology, evolution, and genetics
– Understand the process of evolution by considering differences in gene frequencies
and genotype frequency within a population.
-So evolutionary genetics is also population genetics
Populationgenetics: the study of naturally occurring differences between organisms.
-Differences are genetic variation
Three hierarchical levels:
I) within populations
II) between populations of species
III) between different species
Phenotype with the underlying gene
Phenotype gene unknown
Phenotype and gene both known
– Evolutionary processes are primarily occurring within population. Populations evolve
through changes in allele frequencies. Most, if not all concepts in this course are
important, only in the context of populations, not individuals.
– Genetic variation
– Allele frequency
– Gene flow
– Natural selection
– Genetic correlation Figure2.1– B equals populations. A represents everything including the populations and
is called the meta-population.
We can also consider A as the population and B would be considered as subpopulations ,
demes, or local populations.
Figure2.2– Whitlock in 1992 – fungus beetle – allele frequencies decrease as population
– there is more than one allele at a given locus
– Segregating variation
– polymorphic (many types) means that there is variation
– some loci are fixed - homozygous for the same allele
What makes an allele different?
– E.g.: change/remove intron, change in nucleotide, etc.
– this is called genetic differentiation
– each population could be fixed for different alleles
1. Explain the origin and maintenance of genetic variation
2. Explain the patterns and organization of this variation (why some populations have
more variation than others)
3. Understand the mechanisms that cause changes in allele frequencies
Four agents of evolution:
-drift, mutation, gene flow, and natural selection.
– Determine which alleles are present
– useful for many questions
– mating systems - how inbreed is the population?
– gene flow and population structure –> migration
– determine paternity and heritability (h2)
– generate genetic maps to identify genes underlying complex traits
– conservation genetics
Types of genetic markers
– Visibly discrete polymorphisms
– few distinct morphs – robust to environmental variation
– e.g.: Marine isopod –> paracercius sculptor (Shuster and Wads)
- sponge – within holes of a sponge there were different types of isopods
(crustaceans) for males but only one type of female
- Alpha males – territorial and very successful meeting
– beta males – female mimic not a threat to alpha male because he looks like a
– gamma males – sneaker male - sneaks both males alpha and Beta
– protein, DNA, or RNA
– Many modern methods
– vary – protein allozyme's (first molecular markers)
– what is the source Of these molecular markers? Mutation
– Mutation is the ultimate source of genetic variation. Somatic Germline
– E.g.: tumor, non-heritable (in the absence – heritable
of genetic predisposition of underlying trait) – in the cells that produce gametes.
–– mutation is past to daughter cells but not
sexually produced offspring.
Point mutations Chromosomal
– single bases – change in segment of DNA
– loss, gain, or substitution – – Loss, duplication, or All mutations
rearrangement. are changes in
Terms to know
– insertion/deletion (Indel)
– Richard Lee wanted at Harvard (Gould and Wilson)
– Electrophoresis: smaller things are more faster severe found lower down (see figure
– Allozyme = different enzymes
– homozygous both bands on top of each other appears as one - slow/slow
– heterozygous because bands shown as two separate bands - fast/slow
F(aster) = smaller
S(lower) = larger
How variable are proteins?
Mammals – 15%
Birds – 22%
Insects – 33%
Plants – 25%
Advantage of allozyme's
– cheap, markers, and are codominant (both homozygotes and heterozygotes are
expressed) Disadvantage of allozyme's
– reveals only small amount of variation
– many DNA polymorphisms don't result in change in allozyme
– some amino acid changes don't affect mobility on gel
– enzymes cut DNA at specific sequences (nonrandom)
– sites are often palindromes - reads the same backwards and forwards
– e.g.: ALU I EcoRI
5' AGCT 3' 5' GAATTC 3'
3' TCGA 5' 3' CTTAAG 5'
–usually done at 37°C
–Two individuals both exposed to ALU I and EcoRI
– so if we run on gel electrophoresis then individual one will be slower because it is
– for individual one we see a band at 9 and for individual two we see a band at 4 and 5
– The polymorphism could be very variable so you don't know if the