In-class Literature Assignment #1
“Convergent adaptation of human lactase persistence in Africa and Europe”
Group members: ________________________________________________________________
Work in small groups to answer questions and prompts below. The point here is to understand the various
elements in each of the figures and how the figure as a whole is used to visualize results of the study. You
will turn in one worksheet for per group, but each group member must fill out a portion of the assignment.
Figure 2 – Genotype & phenotype distributions.
1. Compare and contrast the map on the left with the one on the right - how are they the same, or different?
Left shows the geographic distribution of lactase persistence phenotypes, right shows the distribution
of genotypes thought to be associated with those phenotypes.
2. Why is a change in blood glucose measured to determine lactase persistence phenotypes?
Lactose is metabolized into glucose, so blood glucose should increase in individuals with the lactase
persistence phenotype shortly after they are given lactose.
3. When a genotype is given as CC-GT-GC, what exactly does that mean?
This genotype is homozygous for C at position 13907, heterozygous for G/T at position 13915, and
heterozygous for G/C position 14010.
Figure 3
1. Give a brief title for this figure, in your own words.
Genotype-phenotype association
2. Which genotype is most highly associated with lactase persistence (a) at position 14010 in the Kenyan
population, and (b) at position 13907 in the Sudanese Afro-Asiatic population?
(a) C/G, (b) C/C
3. Which genotype at position 14010 is most associated with lactase non-persistence in Tanzania?
G/G
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4. According to (e), in which two populations is the SNP G/C-14010 most highly associated with lactase
persistence?
Kenyan Nilo-Saharan and Tanzanian Afro-Asiatic
5. What does each blue dot in (f) represent? What does the X-axis represent?
- a SNP (single nucleotide polymorphism
- position along the chromosome
Figure 5 – Gene expression assays.
1. In 3-4 sentences, explain how the authors generated the data for the figure and what the results show.
Figure 6.
1. Give a brief title to this figure in your own words.
Linkage disequilibrium/Extended haplotype homozygosity
2. Why do the authors compare homozygosity tracts from people with, versus without, lactase persistence?
Selection for a beneficial phenotype (i.e. lactase persistence) should increase homozygosity in the
chromosomal regions surrounding the beneficial genotype. People who lack this genotype provide a
background (i.e. selectively neutral) measure of homozygosity for comparison.
3. Explain how linkage disequilibrium (LD) and selection result in extended haplotype homozygosity
(EHH).
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