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SNPing Lactose
By: Mandy Butler, Ying-Tsu Loh
and Cheryl Ann Peterson
Three college students walk in an
ice-cream bar. One orders a delicious
100% whole milk milkshake, the other
two orders a Tofutti strawberry
smoothie. Why?
LACTOSE (pre-assess student
understanding)
• Lactose, the primary sugar in milk, is hydrolyzed
by an enzyme called lactase.
• Virtually all humans are born with ability to utilize
lactose but many lose ability to digest lactose by
12 or 13 years old.
• In lactose tolerant individuals, lactase gene is
expressed into adulthood, so eating a milkshake
is a pleasant experience. But in people who are
lactose intolerant, that lactase gene is switched
off after weaning, and the consumption of milk
products can lead to unpleasant effects.
Pre-assess students on SNPs
• Scientists found a SNP in gene in the
Finnish that seems to be correlated with
lactose tolerance.
Examine phenotype vs genotype to find any correlation
Which variant(s) are correlated with lactose tolerance?
What is the dominant phenotype of the Finnish population?
What is the percentage of the genotype of
the total Finnish population?
• What is your conclusion from looking at
the tables?
• How could a SNP change the phenotype
of an individual?
– Obtain some hypotheses or conclusions
Allele Frequencies from NCBI
ALlele FREquency Database
• Link to articles or have students find
articles associated with the study.
• Examine DATA set
• Go to HAPMAP / ALFRED to examine
non-Finnish populations
– What is the genotype frequency at this locus
– Are these populations lactose tolerant
LAB
• Generate primers – have students BLAST
the primers to find the sequence that
should be amplified
• Enter “WebCutter” (Biology Workbench) to
find RE that can cut the sequence
• Determine the sizes that are produced in
either genotypes
• Correlate Genotype with Phenotype