nly about 1/3 of the worldwide adult human population can digest lactose, the sugar found in the milk of mammals. In this activity you will explore the cultural reasons behind this phenomenon. In order to digest lactose, humans need to produce the enzyme, lactase, in their small intestines. Lactase digests the disaccharide lactose into the monosaccharides, glucose and galactose. If a person does not have the ability to produce the lactase enzyme, the undigested lactose goes from the small intestine to the large intestine, where it is digested by bacteria through fermentation. That process results in the production of various gases and acids that can cause discomfort.
The genetic switch that regulates the expression of the lactase gene is active in babies, but not in most human adults. Individuals who are lactose tolerant (or lactase persistent) have a mutation in the lactase switch that keeps the switch turned on into adulthood, so they continue to be lactose tolerant.
Watch the biointeractive movie on the evolution of lactose tolerance: Got lactase? Coevolution of Genes and Culture. Answer the assessment questions that pop up as the movie runs. At the end of the movie, the interactive will generate a report with your answers. You must submit the report to the assignment link in canvas. The report will only be graded for completion. (2 pts)
Got Lactase? Coevolution of Genes and Culture movie with Interactive Assessment: HHMI Got Lactase? Interactive Movie. (Links to an external site.)
Complete a two-part worksheet with a pedigree analysis and DNA sequence analysis and upload your text answers to canvas in the assignment link (10 pts).
You will analyze the Finnish family pedigree that was presented in the Got Lactase? movie to understand the pattern of inheritance of lactose tolerance and intolerance. You will also examine portions of the DNA sequence near the lactase gene to identify the specific mutation associated with lactose tolerance.
Are you lactose tolerant or intolerant? What is it, biologically, that makes you that way? Based on what you know about how this trait is inherited, what do you know about your genotype and the possible genotypes of your parents?
Voicethread prompt #2:
Examine the map from the movie (below) or go to the following website to see lactose intolerance statistics by county: https://milk.procon.org/lactose-intolerance-by-country/ (Links to an external site.)
Which regions of the world have the highest lactose tolerance? Which have the lowest? Where would you expect to find evidence of early cultures using animal milk as a food source? Why is lactose tolerance much higher in some groups and extremely low in others?