Gene-Culture Coevolution Lactase Persistence Flashcards
What is lactose?
‘milk sugar’ - the prime source of carbohydrates for all young mammals
Why can’t lactose itself be absorbed by humans
lactose is a disaccharide and it must be hydrolyzed into two monosaccharides.
How is lactose digested in the body
with digestive enzyme Lactase: hydrolyzed into galactose and glucose
Why is lactase non-persistence the ancestral state for humans?
in the Palaeolithic there were no herds kept, so no milk was drank at older ages
Why do people that can’t digest lactose get gastrointestinal discomfort
Lactose gets fermented by bacteria in the colon, producing gases resulting in abdominal distention and flatulence (farting).
Lactose osmotically attracts fluid into the bowel causing diarrhea.
What regions of the world have the most lactose intolerance
East and southeast Asia, Africa, south America and the Arctic
T/F people are born with lactose intolerance
false, it occurs after childhood
The most common food allergy in infants and young children
Cow milk protein allergy
What makes milk allergy different from milk intolerance?
milk allergy - an immune response to milk proteins
intolerance - inability to digest lactose
What is lactase persistence and what determines it
- continued production of lactase after childhood
- is a genetically determined dominant trait
Lactase non-persistent phenotype is
homozygous - receives two copies of the low lactase-activity allele (ancestral allele)
Lactase persistent phenotype only needs
one copy of the high lactase-activity allele from their parents
Lactase persistence likely only reached appreciable levels in some populations in the last
7,000 years
how do we know that different lactase persistence gene variants produce the same phenotype?
The european gene variant is different from the lactase persistence gene variant in African cattle herders.
Pastoralism is
a way of life centered around herding and raising livestock
