Question

Please answer all fo the following questions.

1. Describe a population where you would expect to find a low frequency of adult lactose tolerance.

2. Why is adult lactose tolerance infrequent in that population?

3. Describe a population where you would expect to find a high frequency of adult lactose tolerance.

4. Why is adult lactose tolerance frequent in that population?

Answer 1

Lactose intolerance is a digestive disorder caused by the inability to digest lactose, the main carbohydrate in dairy products.The lactase enzyme is needed to break lactose down into glucose and galactose, which can then be absorbed into the bloodstream and used for energy.

Before fresh animal milk was readily available, humans did not need to digest milk after they were weaned. However, the domestication of mammals approximately 9,000 years ago presented humans with the first opportunity to drink fresh milk throughout life. This provided a potential selective force for lactase persistence, whereby high levels of intestinal lactase, the enzyme that digests lactose, persist into adulthood. Individuals without significant levels of lactase are lactose intolerant, and the frequency of lactose tolerance varies between populations.

1.The prevalence of lactose intolerance is lowest in populations with a long history of dependence on unfermented milk products as an important food source. For example, only about 5 percent of people of Northern European descent are lactose intolerant.

2.Northern Europeans have a long history of fresh milk consumption, and they were the only population with a low frequency of lactose intolerance. North Europeans have the gene diversity of ancient non Africans who migrated from Africa to rest of world and  developed a taste for fresh milk as it became available through the domestication of animals. Northern Europeans also have an unusually high frequency of one particular set of DNA sequence variations, known as a haplotype, at the lactase locus. Studies also proposed that this haplotype is common in the northern Europeans because it is associated with the ability to digest milk.

3. Approximately 65 percent of the human population has a reduced ability to digest lactose after infancy. Lactose intolerance in adulthood is most prevalent in people of East Asian descent, with 70 to 100 percent of people affected in these communities. Lactose intolerance is also very common in people of West African, Arab, Jewish, Greek, and Italian descent.

4.These populations might have the gene diversity of the ancient native Africans who did not consumed milk as an impotant food source.