Milk – How Sweet Is It? Lab

Sample
Numbers / Ancestral Country of Patient / 2” Glucose levels
(mg/dL)
Patient #1 / Japan
Patient #2 / Kenya
Patient #3 / China
Patient #4 / Italy
Patient #5 / Papua
New Guinea
Patient #6 / Finland
Patient #7 / Saudi Arabia
Patient #8 / Uganda
  1. Study your glucose indicator reference chart. The indicator only changes color when glucose is present. Milk contains the sugar lactose, so a lactose intolerant person will not have his/her indicator change color. A person that is able to digest milk will be able to convert the lactose to glucose, so his/her indicator will change color.
  2. What color will the indicator strip be for a person who cannot digest milk (lactose intolerant)?
  1. What color will the indicator strip be for a person who can digest milk (lactase persistent)?
  1. Which patients appear to be lactose persistent (able to digest milk)?
  1. Which patients appear to be lactose lactose intolerant?
  1. What further questions do you have based on the class results?

Global Distribution of Lactase Persistence Genotype

High levels of lactase persistence (able to digest milk) green
Low levels of lactase persistence (lactose intolerant) red

Read the directions for analyzing your population data. The directions are on the back of the “Milk…How Sweet Is It?” directions

  • Using red & green pencil, complete the key for the global map
  • Using pencil dots, indicate areas with high% of population with lactase persistence (can drink milk) with green, and areas of low% lactase persistence (lactose intolerant) with red
  1. Looking at the global distribution of red & green stickers on the map, write three things that you notice about the global distribution of lactase persistence. Note patterns, exceptions to those patterns, or generalizations you can make from the data.
  1. What trends did you notice in the class data for each patient? Are they consistent with the stickers on the class map?

“Lactose Intolerance: The Co-Evolution of Genes & Culture” video

  1. What profound cultural changes occurred about 10,000 years ago that had a major biological impact on our species?
  1. All infant mammals can digest milk, but what happens when they stop drinking milk? The only mammal group that can tolerate milk past infancy are some humans – why do you think that is?
  1. About how many adult humans worldwide can digest milk? Are they the norm, or the exception to the rule?
  1. Explain how the lactase persistence mutation has come about using evidence from culture, genetics, and historical discoveries to support your explanation.
  1. Being able to digest milk is considered an adaptation, or selective advantage. What might be some advantages to being able to digest milk?

6. Complete the “After” column of your warm up.

Look at the statements where your answer changed after watching the video. Which of those statements surprised you most? Explain why.

Reflection Questions

  1. If lactose intolerance did not cause any symptoms, lactose-intolerant individuals would be able to use milk as a source of protein. Explain why it is possible for them to digest the proteins in milk even though they lack the lactase enzyme.
  1. Explain how lactase persistence is a good example of gene-culture co-evolution using evidence from the activity to support your explanation.
  1. Based on your knowledge of natural selection, predict how frequency (%) for the gene for lactase-persistence (ability to digest milk)might change if the same populations are sampled again in 1000 years.
  1. The study did not include data from the United States. What would you predict the map of the United States to look like (as far as where the green and red stickers would be) and why?

Adapted from