College aantekeningen

Summary Evolutionary Medicine

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Vak
Evolutionary Medicine (WBBY03905)

Instelling
Rijksuniversiteit Groningen (RuG)

Boek
Brock Biology of Microorganisms, Global Edition

This summary covers: - A review of evolutionary genetics and dynamics - The co-evolution of parasites and hosts - Evolution of the immune system - Evolution and origin of human infectious diseases - Evolution of virulence – why are some infectious diseases fatal and others so mild that they ...

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Geupload op 12 april 2022
Aantal pagina's 29
Geschreven in 2020/2021
Type College aantekeningen
Docent(en) M.g. elliot
Bevat Alle colleges

selection
gene flow
genetic drift
evolution
genome size
red queen hypothesis
arms race
trade offs
genomic imprinting
kochs postulates

Titel boek:Brock Biology of Microorganisms, Global Edition

Auteur(s):Michael T. Madigan, Kelly S. Bender

Uitgave:maart 2018
ISBN:9781292235103
Druk:15

College aantekeningen
Summary of Host- and Microbe Interactions
Samenvatting
Samenvatting Brock Biology of Microorganisms, Global Edition, ISBN: 9781292235103 Microbiology
Samenvatting
Samenvatting Brock Biology of Microorganisms, Global Edition, ISBN: 9781292235103 Bacteriën, Virussen En Biotechnologie (BVB)

Instelling
Rijksuniversiteit Groningen (RuG)
Studie
Biology / Life Science And Technology
Vak
Evolutionary Medicine (WBBY03905)

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Lecture 1
Beukeboom (chapter 1)

Introduction to evolutionary thinking

1. Genetic variation
2. Natural selection
- Not only surviving of the fittest but also
reproduction has to take place
3. Adaptation
- Trait that increases the ability of an organism to
survive and reproduce in specific environments
(Darwinian fitness)
4. Evolution
- A change over time in the genetic composition of
a population
- For this genetic variation is needed

Four necessary conditions for natural selection to act

1. Variation in the trait of interest
- Mice with different fur colours that are able to adapt better to different environments
2. The trait is heritable
- Almost all traits have the effect of the environment
- Come about through a combination between genetics and environment
3. Variation in reproductive success
- There is always reproduction and reproductive success
4. Some need a higher or lower reproductive success then others depending on the non-zero
correlation trait
- So the mice which are eaten the most by birds, because of fur colour, have to reproduce
at a higher rate in order to maintain their population

Forms of selection
- Sexual reproduction generates variation
- Asexual reproduction (clones)
o Offspring identical to parents except for
mutations
- 1 locus, 2 alleles
- Positive (directional) selection: selection against a
recessive lethal allele
o Directed to extreme alleles
o Increases the beneficial alleles
- Disruptive selection
o Both extreme alleles (homozygotes recessive or homozygotes dominant)
- Stabilizing selection
o Heterozygotes is in advantage
- Frequency-dependent selection
o Bright colours  dangerous traits, but they are preferable by females
o Positive: fitness increases when the frequency increases
o Negative: fitness decreases when the frequency increases

,Linkage disequilibrium = alleles are assorted according to their frequency in the population
- Reduced by recombination – recombination restores the equilibrium
- The combination of alleles are as what you would expect based on their frequency of the
population if there are no other factors (selection, environment) involved
- Locus A can have allele A or a
- Locus B can have allele B or b
- Crossing you would expect AA, Aa, aa
- If this is not the case  disequilibrium
- The case of Crohn’s disease  recombination decreases frequency
- Depends on physical distance, chromosomal position and configuration
o Increase in distance between genes causes an increase in disequilibrium and less
recombination
- Selective sweep = change in frequency of an allele due to selection on a closely linked
locus (also called hitchhiking)
- G6PD locus  glucose-6-phosphate dehydrogenase deficiency  helps against malaria
and therefore more present in African countries

Natural selection and evolutionary thinking
- Most of the time a very long process
- In some cases however it can be studied over a shorter period of time (bc changes and
adaption in some cases occur faster)
- Natural selection doesn’t have a goal to save a species in the future, but it can only work
backwards and work with the traits and variation already present
o Tinkering old pots together again to make one good new one

The study of evolution entails:
- Analysis of factors that change the number of copies of a gene in a population as they are
passed on (population genetics)
- Analysis of how genes produce traits that interact with the environment and therefor can
change (how genotype influences phenotype)
- The variants that persist aren’t necessarily the best possible
o Natural selection can only be applied on the traits that are already available
- Fitness = relative reproductive success

Five agents of evolutionary change

- Mutation

, - Gene flow
o Migration by individuals, take genes with them when moving to new population
- Non-random mating
o Increases the degree of homozygosity
o Increase in change of diseases
o 50% increase in homozygosity within one generation when there is 100% self-
fertilization
- Genetic drift
- Selection

Evolution of HIV
- Intracellular parasite of human macrophages and T-cells of immune system (uses cells
(infect it) to copy itself and kill the host cell)
- Immune cells start making copies of the virus
- There is a particular protein on the membrane of the T-cell which recognizes the binding
protein of the HIV virion, which allows the virus to enter the cell
- HIV RNA molecule is released in the host cell
- HIV reverse transcriptase makes RNA into DNA
- Treatment: azidothymidine
o Prevents binding of the next base by carrying N3  the virus cannot replicate
anymore
o Increased resistance to this drug by small mutations in reverse transcriptase,
which could detect the difference between regular thymidine and AZT
o Now get a variant through mutations which is partly resistant to AZT

Host-parasite interactions
- Virulence versus resistance
- Host
o Small population size
o Long generation time
o Low mutation rite
- All reverse for the parasite

Lecture 2 genome structures Beukeboom
Genome evolution = changes in genomic sequence, structure and function
- Point mutations
- Indels = deletions and insertions
- Synonymous = silent substitutions
o Faster rate
o No amino acid change
o Still encodes for the same proteins
- Non-synonymous = replacement substitutions
o Depends on protein complexity

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