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Lecture 2

BIO220H1 Lecture Notes - Lecture 2: Lactose Intolerance, Lactase, Coevolution


Department
Biology
Course Code
BIO220H1
Professor
John Stinchcombe
Lecture
2

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Lecture 2 midterm notes
2 custom cultures in human:
Matrilocality and Patrilocality variation and genetic differences
Females are moving and constantly moving population females come from
multiple locations to one particular location
Genetic differentiation graph: (you are considering the differences in genes measuring
diversity)
- Measures allele frequency differences between populations
- Further apart geographically, there is no trend for autosomes
- Y chromosome greater difference the farther that they are
- * female migration so the Y chromosome between population greater
Genetic markers to UNDERSTAND FITNESS
o combine knowledge of genetics + behavior genetic differences
o human social behavior affects pattern of differentiation
reduced genetic diversity for the sex that stays WITHIN a population
o reduced Y chromosome variation if the male stays WITHIN population
o reduced mtDNA if the female stays WITHIN population
Human Agricultural Co-Evolution: this is co-evolution
o Natural selection imposed by our agricultural practices and leaves
imprint in our genome
- Reciprocal evolution one imposes selection on the other
The evolutionary response imposes selection on the opposite species
Co-evolution between sexes and species
Reciprocal response in our evolution and agricultural species
The species that we use for our agricultural purposes
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How do we as humans co-evolve with our agricultural species?
o Evolution occurs by natural selection
o Ecology is our culture and the organisms that we interact with
o Genetics provides the information that is transmitted through evolution
Culture does include diet, choosing a partner, etc…
This leaves an imprint on our genome
Humans specially infants rely on milk, milk is digested by lactase enzyme
The product in the milk is lactose, and is digested by the enzyme lactase which breaks the
lactose down into glucose and galactose
- Sugars we use and burn for energy
- Lactase production declines in adulthood, so we can stop digesting milk and its
products
o The wild condition is the decline in the production of the lactase enzyme
this leads to lactose intolerance
The exception: Northern European origin
CONSIDERING THE CATTLE THAT WE USE:
o European people lactase production persists and so they can continue to
digest milk
o Chance (genetic drift? Stochastic) or natural selection (deterministic)?
Does this affect the cows?
There was a high correlation between the changes in genes for lactase pesistane and the
ability to digest milk
The hypothesis:
1) LACTASE GENE FAVOURED BY NATURAL SEELCTION
2) SUBSTITUTIONS ARE CAUSAL VARIANTS (substitutions caused by NTP’s
etc…)
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