Case Study: The world wide
distribution of lactose intolerance
University of Kentucky:
Andrew Bouwma
Peter Mirabito
Jeffrey Osborn
Stanford University:
Shyamala Malladi
Patricia Seawell
University of Miami:
Douglas L. Crawford
Marjorie F. Oleksiak
Facilitators:
Kimberly Tanner,
San Francisco State Univ.
Langdon Martin,
Univ Wisconsin
Classroom Setting
• Sophomore Genetics Course
• Students have been introduced to
Genes
Molecular Mechanisms of Transcription
Transcriptional Regulation
Molecular Mechanisms of Translation
Translational Regulation
Learning Goals –
Students will understand
Measurable Outcome
Students will be able to
(1) the concept of a gene
- Sketch a representation of a gene and label its parts (promoter, intron,
exon, termination signal)
- Relate Mendel’s inheritable traits to a gene
(2) the mechanism of transcription
- List, order and define the active players in transcription (or diagram)
- contrast the structure of nuclear DNA and hnRNA with cytoplasmic
mRNA
(3) the regulation of transcription
- how does exercise lead to larger muscle mass
- predict which genes might be expressed under conditions of exercise or
hypoxia (low blood oxygen)
- how does eating more sugar lead to more absorption of sugars
(4) the mechanism of translation
- Generate a strip sequence that describes the process/mechanism of
translation
- Describe how some antibiotics kill bacteria
(5) the regulation of translation
(6) how genes affect phenotypes
- compare and contrast global vs mRNA specific regulation
- imagine five ways that protein synthesis can be regulated
- explain how skin becomes darker when exposed to the sun
- describe how DNA affects the production of hemoglobin
- - explain why a person of northern European descent can drink milk,
while a majority of the world population cannot
(7) and engage in specific components
of the scientific process.
- read and interpret biogeographical maps
- read and apply appropriate information from the primary literature to a
scientific problem or question.
Learning Goal
6) Genotype  Phenotype
7) Engagement in the Scientific Process
Outcomes:
• Interpret the biogeographical maps
• Read and apply appropriate information from
the primary literature to address a scientific
problem.
• Students will explain why specific populations
maintain the ability to drink and digest milk
through adulthood.
What do you think is the percentage of adults
around the world who are lactose intolerant?
A:0-20%
B: 20-40% C: 40-60% D: 60-80% E:>80%
Lactose and Lactose Intolerance
Lactose is milk sugar, a disaccharide in all
mammalian milk
Lactose intolerance is the inability to digest lactose,
because of a lack of the required enzyme lactase in
the digestive system.
 Drinking milk without having an active lactase
enzyme produces gastro-intestinal distress
(e.g.,diarrhea).
It is estimated that 75% of adults worldwide show
lactose intolerance.
Adult Worldwide Milk Intolerance
due to the Inability to Digest Lactose
Milk
Intolerance
Native Americans
Aboriginal Australians
Adapted from http://en.wikipedia.org/wiki/Lactose_intolerance
Adult Worldwide Lactose Intolerance
Milk
Intolerance
What do these data say about the worldwide
distribution of the ability to drink and digest milk
as an adult?
Think & Write
Pair-Share
1 minute
2 minutes
Predict
What would you predict is the relationship
between the world wide distribution of adult
and infant lactose intolerance?
A: Same
B: Opposite
C: Unrelated
D: Same except for North America
Milk
Intolerance
Discuss
Convince your neighbor and revote
What is the relationship between the world wide
distribution of adult and infant lactose
intolerance?
A: Same
B: Opposite
C: Unrelated
D: same except for North America
What is the relationship between the world wide
distribution of adult and infant lactose intolerance?
Frequency of Lactose Intolerance in Infants
Milk
Intolerance
>90% Tolerance
Brainstorm
Given these data:
75% of adults worldwide cannot drink and
digest milk
Yet nearly all infants are able to digest milk
Propose molecular mechanisms to explain why
only a few populations have the ability to drink
and digest milk throughout adulthood.
Choose a hypothesis
•
•
•
•
•
The molecular mechanism that explains why only a
few populations have the ability to drink and digest
milk throughout adulthood includes variation in:
A: the coding region of the lactase gene
B: the regulatory region of the lactase gene
C: transcription factors
D: the post-translational modification of the enzyme
lactase
E: None of the above
For your final assessment
• Read the Genetics paper on “Lactose
Intolerance”
• Write a short essay (250 words) to defend one
hypothesis and refute one other
> Paper will be posted on Blackboard.
> Potential hypotheses will be posted.
> Biogeographic map will be posted.
Activity/Assessment
Topic
Time
Clicker
Think about people you know who are
lactose intolerant
1 minute
Map Interpretation
Analysis of biogeographical data
2 minutes
Think and Write
Pair-Shore
How much diversity is there in lactose
intolerance
3 minutes
Clicker
Predict infant milk intolerance
1 minute
Clicker
Discuss and revote
2 minutes
Brainstorm and write
Propose molecular mechanisms to
explain lactose intolerance
1 minute
Clicker pre-assessment
Vote on molecular mechanisms to
explain lactose intolerance
1 minute
Final assessment
Defend and refute hypotheses
Homework
Diversity:
Not using red-green map colors
Population diversity
Teaching methods addresses a diversity of learning styles
Possible discussion of “Got Milk”