BIO220 Lecture 13 Flashcards
Human-agricultural coevolution
define: coevolution
reciprocal evolutionary responses in a pair of species, caused by selection imposed by each other
define: sexual coevolution
reciprocal evolutionary responses in the 2 sexes, caused by selection imposed by each other
- e.g. mate selection
human agricultural coevolution
reciprocal evolutionary responses in humans & their agricultural species, caused by selection imposed by each other
human agricultural coevolution is driven by…
culture
- agriculture
- husbandry
- passed down from generation to generation through culture
in humans, __ can drive coevolutionary change
culture
evolution by natural selection is a ___ and ___ process
genetic & ecological
Why is evolution by natural selection a genetic & evolutionary process?
- ecology provides selection
- genetics provide the material that is transmitted across generations
for humans, ecology includes…
- culture
- organisms that we interact with
what is used to digest milk
lactase enzyme
what reaction does lactase catalyze?
lactose -> glucose + galactose
wild type for lactose digestion
lactose intolerant
- except people of N. Europe origin
Opposite of lactose intolerant
lactase persistence
which cultures that was studied showed lactase presistence?
- N. Europeans (dairy farming)
- African cultures (mobile dairy farming)
Define: genetic drift
variation in the relative frequency of different genotypes in a small population
Why are small populations subject to genetic drift?
random sampling of genes
- such a small population size, so maybe only 1 individual has a trait, and they die
chance vs. determinism: genetic drift
chance
chance vs. determinism: natural selection
determinism
how do we tell if something is deterministic or due to chance?
if independent events have the same results over and over again, it’s probably deterministic
define: convergent evolution
independent evolution of the same trait in different groups (populations, species)
___ evolution provides evidence for natural selection
convergent
Does convergent evolution act on the same / different genes?
Open question, can be both
- lactase example was same gene
___ humans were unable to digest lactose as adults
Neolithic
When did lactase persistence appear?
after the appearance of dairy agriculture
In African cultures, mutations in lactase is associated with…
lactase persistence into adulthood
example of convergent evolution
lactase persistence into adulthood
How do we examine imprints that coevolution has left on human genomes?
apply principles of population genetics
population genetics
compare patterns of genomic variation that is seen in current group vs. completely neutral model
non-synonymous mutations
mutations that change AA
synonymous mutations
mutations that do not change AA
we would expect ___ genetic variability in the regions of the genome that experience more selection
less
we would expect there to be ___ differentiation between populations at sites that experience more selection
more
effect of neutral mutations on synonymous vs. non-synonymous mutations
- protein function is not changed
- same rate of synonymous and non-synonymous mutations
- dN/dS = 1
effect of deleterious mutations on synonymous vs. non-synonymous mutations
- more mutations = lower fitness
- synonymous mutations favoured
- dN/dS < 1
effect of beneficial mutations on synonymous vs. non-synonymous mutations
- more mutations = higher fitness
- non-synonymous mutations favoured
- dN/dS > 1
Approx ___ sites in a gene sequence are replacement sites
3/4
how to predict DNA difference b/t species?
- Align gene sequence
- Evaluate dN/dS ratio
*3/4 are assumed to be synonymous mutations (estimate) - this makes calculations fair
define: genetic hitchhiking
as beneficial mutations spread, they drag their nearby mutations along
consequence of genetic hitchhiking
genetic variation in areas of beneficial mutation goes down
what determines the region size that is affected by genetic hitchhiking?
rate of recombination
what does recombination do to genetic hitchhiking?
- breaks things up
- lots of recombination = small area where genetic diversity is low
lactose persistence has higher / lower variability than lactose intolerance? Why?
lower; selected on by natural selection
what has the evolution of lactose persistence done to cows?
select for milk production -> reduced genetic variation in the milk producing genes
starch digestion
polysaccharides -[amylase]-> maltose -[maltase]-> glucose
which gene encodes amylase enzyme? How many copies of it do we have?
AMY1
Many copies in the genome (2-12)
More copies of AMY1 means…
more amylase can be made
humans vary in the ___ of the AMY1 gene
number of copies
in the AMY1 study, why can we eliminate environmental variability?
because we are looking at gene copy numberf
In the amylase study: what is imposing selection on what?
Cultural behaviour (how much starch in diet) impose selection on humans (copies of AMY1 gene)
Siberian Yakut have low / high starch diets
low
AMY1 number should be the most different between which groups?
populations that eat low starch vs. populations that eat high starch
diarrheal disease cause __% of deaths in children
15
we use __ to scan the genome for regions responsible for co-adaption. What do we look for?
population genetic principles.
look for regions in the DNA where there is large similarity between populations. This is where natural selection forces have acted.
What do we use genetic principles to do?
look for regions responsible for co-adaption in the genome.
