Week 2 Gene-Culture Coevolution Lactase Persistance

Question 1

What is lactose?

Answer 1

it is a disaccharide formed from two monosaccharides sugars of glucose and galactose

• milk sugar lactose - prime source of carbohydrates for all young mammals, including human infants which is the first sugar we are exposed to.

Question 2

how is lactose digested?

Answer 2

lactase (B-galactosidase) in the intestine hydrolyzes lactose so the glucose can be absorbed since lactase cannot be absorbed itself.

Question 3

What is lactase non-persistance?

Answer 3

Condition where you can no longer after childhood cleave lactose into its two monosaccharide sugars because you know longer produce the enzyme

• continued production of lactase after childhood is a genetically determined trait
• most populations the ability to digest alctose ceases in childhood
  
  • 3-5 years ability diminishes
  • 7-10 intestine no longer produces lactase

Question 4

What happens if you cannot digest lactose?

Answer 4

• lactose gets fermented by bacteria in the the colon and produces gases such as CO2, methane, hydrogen
• lactose osmotically attracted fluid in the bowel lumen causing bloating, diarrhea, flatulence, watery stools

Question 5

What is lactase persistence?

Answer 5

• lactase persistance is the genetically programmed continued activity of the lactase enzyme into adulthood
  
  • allele that continues
• it is a dominant trait: only one copy of the allele required for expression of the phenotype

Question 6

How did lactase persistance arise?

Answer 6

• the trait arose independently worldwide several thousand years ago
  
  • different mutations produce the same phenotype
  • european mutation gene variant is different from the lactase persistence gene variants in Africa cattle herders
• Lactase persistence likely only reached appreciable level in some populations in the last 10,000 years
  
  • animal domestication
  • dairy farming
  • selective advantage

Question 7

How does lactose intolerance vary globally?

Answer 7

Question 8

where is lactose tolerance prevalent?

Answer 8

highest in populations with a long history of consuming milk products

• took what was available in environment

Question 9

What are the two hypothesis for lactase persistence?

Answer 9

Question 10

gene-culture coevoltion of lactase persistance and bacterial fermentation of milk products

Answer 10

evidence of fermented milk products exist such as yogurt and cheese and have been produced since around 10,000 BCE

• About time of the neolithic revolution. Can look at pottery used to hold liquid and can determined the kind of liquid that they held.
• individuals may lack the lactase allele but can still tolerate dairy products in which lactose in broken down by the lactic acid fermentation process
  
  • people were probably not consuming fresh milk especially since it went bad quick and was hard to preserve rather it would be converted into the dairy products
  • lactic acid bacteria ferment lactose to produce lactic acid

Question 11

Is there an evolutionary advantage to being able to consume milk and dairy products?

Answer 11

• Ca for skeletal integrity
• milk is relativelt clean liquid
• multiple nutrients (vitamins A, D, B12; riboflavin, Ca, phosphorous)
• Energy, fat, protein
• rather than killy animals for meat your eat them

Question 12

Why is milk important for skeletal integrity?

Answer 12

• Ca is an important mineral for skeletal integrity
• over 99% of body Ca is calcium hydroxyapatite in bones and teeth
• High Ca bioavailability in milk
  
  • soy milk and tofu fortified with Ca
• Vitamin D is in fresh milk and it increases Ca absorption in small intestine, increases Ca reabsorption in the kidney and increases bone mineralizartion