Got Lactase? The Co-evolution of Genes and Culture
Watch this video on Lactose intolerance and co-evolution of genes:
https://www.biointeractive.org/classroom-resources/making-fittest-got-lactase-co-evolution-genes-and-culture?playlist=183781
KEY CONCEPTS • During digestion, food is converted into simpler molecules that can be absorbed and used by the body. For example, milk is digested by the enzyme lactase, which breaks down lactose (a sugar in milk). • Humans, like all species, evolve and adapt to their environment through natural selection. Lactase persistence is an example of a human adaptation. • For evolution to occur, there must be selection for or against traits. Both the physical and cultural environment can affect selective pressures. The cultural practice of dairying provided an environment in which lactase persistence was advantageous. • Different mutations can produce the same phenotype, and similar phenotypes can evolve independently under similar selective pressures. For example, lactase persistence arose independently in African and European populations due to different mutations. • Mutations can occur in regulatory regions that determine when and where a gene is expressed. Mutations giving rise to lactase persistence are in a “switch” region that regulates expression of the lactase gene.
Answer the following questions and submit it for credit:
1. When the enzyme lactase breaks down the sugar lactose, which two simpler sugars are formed?
a. glucose and fructose
b. galactose and maltose
c. glucose and galactose
d. glucose and maltose
2. In the film, geneticists discovered that the difference between lactase-persistent (lactose-tolerant) and
lactase-nonpersistent (lactose-intolerant) people was due to a mutation. This mutation was not in the part
of the lactase gene that encoded the lactase enzyme. In which of the following was the mutation located?
a. the genetic switch for the lactase gene
b. an intron of the lactase gene
c. the gene for glucose production
d. different genes for different individuals
3. Which statement most accurately describes human evolution?
a. Humans stopped evolving 200,000 years ago when they became a distinct species (Homo sapiens).
b. Humans stopped evolving after adapting to a pastoralist way of life.
c. Humans are still evolving and will continue to evolve through natural selection.
d. Human evolution through natural selection ended with the development of modern medicine.
4. Scientists hypothesize that the use of milk in pastoralist cultures drove the evolution of lactase persistence.
Which discovery best supports this hypothesis?
a. The lactase gene is present both in humans and in domesticated animals.
b. Ancient pots used to hold milk are about the same age as the lactase-persistence mutations.
c. Most human cultures today drink milk, and most people worldwide are lactase persistent.
d. Scientists have identified different mutations that cause lactase persistence
