Exam 2: Got Lactase? The Co-evolution of Genes and Culture

Which statement accurately describes human evolution?

Humans are still evolving and will continue to evolve through natural selection.

Lactose intolerance is an allergy to milk and milk products.

False, the genetic switch for lactase production is turned off, not allowing digestion of milk and products.

Throughout human history, people have always consumed the milk of other animals.

True, because ever since the trait for lactose consistency existed, it coincided with storage of milk from pastoralists that rely on animals for milk.

Lactose intolerance is a genetic trait.

True, because the genetic switch being left on or off determines lactose intolerancy or lactase consistency.

Baby mammals depend on milk to survive.

True, because the genetic switch to produce lactase allows them to receive milk from mother in order to receive nutrition and survive.

Digesting lactose causes a person's blood glucose levels to increase.

True, because when lactose is digested by lactase in small intestine, glucose enters the bloodstream.

Lactose is a sugar in milk.

True, this is a fact.

Why would measuring blood glucose levels in an individual, 20 to 30 minutes after they drink a liter of milk, indicate whether they are able to digest lactose.

When lactose is digested by lactase, the glucose that is produced enters the bloodstream from the small intestine.

Which discovery supports the hypothesis that evolution of the lactase persistence trait was driven by the use of milk in pastoralist cultures?

Ancient pots used to hold milk are about the same age as the lactase persistence mutations.

Milk is a healthy food for an adult cat.

False, because the genetic switch for lactase goes out after infancy, and the adult cat won't be able to digest the milk.

Most human adults around the world can digest the lactose in milk; a minority of people cannot digest lactose.

False, most humans (2/3) cannot, only 1/3 can.

What two monosaccharides (simpler sugars) are formed when the lactase enzyme hydrolyzes lactose?

glucose and galactose

Geneticists studying the gene for lactase did not find any differences in the coding region DNA (the section of DNA with instructions to make the protein) between people who could digest lactose and people who could not digest lactose. After they investigated further, they discovered that the difference between lactose tolerant and intolerant individuals was due to a mutation located in

the genetic switch for the lactase gene