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Chapter 2

BIO220H1 Chapter Notes - Chapter 2: Lactase, Anemia, Amylase


Department
Biology
Course Code
BIO220H1
Professor
John Stinchcombe
Chapter
2

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BIO220 article 2
Changes to our genome imposed by diet:
Genetic adaptation to new diets has occurred since the agricultural revolution:
Early farmers had anaemia, this was indicated by archaeological records
Went from hunter-gatherers to farmers due to disease burdens, and farmers have
not adapted to their diets yet causing deleterious digestive disorders
regulation of food metabolism has contributed to a human adaptation to a changing
diet
increase of starchy food intake resulted in more expression of the gene encoding
enzyme responsible for starch hydrolysis
o Populations with higher starch diets had a higher copy number of AMY1
which is the genotype for amylase concentration in saliva
AMY1 low copy number is the ancestral state in humans since chimpanzees have
a much lower concentration of amylase in their saliva than humans
Human groups independently acquired the extra copies of AMY1 by POSITIVE
SELECTION
convergent evolution favours lactase persistence in humans
1) Without amylase, and lactase, starch and lactose have detrimental effects.
2) Energy-dense diet is essential during pregnancy and childhood, this supports
neonatal survival rates
3) Insufficient digestions prevented profit, and farmers that could naturally digest it
were at an advantage
AMY1 is variable in terms of copy number, new copy number in response to selection
pressures
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