Answer Happy

Exercise 8 variation in the ADH1B Gene
The ADH1B gene is one of the genes that codes for alcoholdehydrogenase (ADH) - an enzyme that helps in the digestion ofalcohol. A variant of this gene, called the ADH1B*47His allele,helps metabolize alcohol faster than other variants of the gene,thus reducing the amount of alcohol that saturates the bloodstream.It also causes a negative side effect, where a person’s faceflushes red when he or she consumes alcohol. This allele is rarelyfound in African or European populations, but it is very frequentin East Asian populations, where it is often found in more than 50%of the populations and may even be found in almost 100% of peoplein certain populations. These East Asian populations also have ahistory of growing rice and making fermented rice beverages thatextends as far back as 12,000 years before the present (BP). Themap below shows the frequency of the ADH1B*47His allele in EastAsia. Sites where evidence of rice cultivation has been found aresuperimposed on the map.
Given what you know about the evolutionary forces behind humanvariation, how would you explain the distribution of theADH1B*47His allele? Why do you think this allele is common in EastAsian populations? Do you see a relationship between ricecultivation and allele frequency? Hint: consider the benefits anddrawbacks of consuming alcoholic beverages and how this mightfactor into the evolution of the ADH1B*47His allele.
Age of rice cultivation sites 12,000-8,000 years BP 8,000-6,000 years BP 6,000-3,000 years BP Percentage of population with ADH1B*47His allele 0 10 20 30 40 50 60 70 80 90 100