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Human Digestive System

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Got Milk?
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Got Milk?

The Zebu is a common type of livestock in tropical climates

Topic

Lactose Intolerance

Student Exploration

The Dairy Convergence

Lactose intolerance is probably familiar to most of you. Normally, organisms lose the ability to digest milk as they grow to adulthood. This lack of tolerance has little effect on most organisms as there really is no milk source for them as adults. However, the case with Homo sapiens is a little different. A ways back in our history, some humans took to raising livestock to supplement their diet and with this change in behavior a new resource became available, along with a benefit for anyone who could exploit it. As you may have surmised, this new resource was milk and all the products which can be made from milk. Today 50% of adults can tolerate the lactose found in milk and milk products. Researchers are looking at how this ability developed to learn more about the adaptability of humans as a species and possibly help those people who are lactose intolerant.

Extension Investigation

Use the resources below to answer the following questions:

  1. Does having lactose intolerance mean that you cannot tolerate any lactose at all? How did this situation help lactose tolerant genes increase in the human population?
  2. What kind of mutation in chromosome 2 was found to convey lactose tolerance into adulthood? Are you surprised that such a mutation could cause such a big change? Why or why not?
  3. Is the new East African mutation the same as previous mutations found in Middle Eastern and European populations? Why is it believed these types of mutations were selected for in human populations? What evidence is there to support this hypothesis?

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