Got Lactase? Quiz Results

1. The primary sugar in milk is lactose. The enzyme lactase breaks lactose down into which compound(s)?

  1. glucose only
  2. fructose only
  3. glucose and galactose
  4. fructose and galactose

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2. How would a biologist describe someone who is "lactase persistent"?

  1. Someone who is able to digest lactose as an adult.
  2. Someone who is unable to digest and tolerate lactose as an adult.
  3. Someone who is unable to digest and tolerate lactose as a child.
  4. Someone who is able to digest and tolerate lactose as a child but who loses the ability as an adult.

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A line graph showing four individuals' blood glucose levels over time. The x-axis is in minutes, ranging from zero to sixty in intervals of 15 minutes. The y-axis is blood glucose levels measured in milligrams per deciliters, ranging from 80 to 160. Peter, Rachel and Arthur start with a blood glucose level at approximately 95. Sarah begins with a blood glucose level or approximately 108. Sarah and Peter’s blood glucose levels rise and peak around 45 minutes, with Peter’s measuring approximately 155 milligrams per deciliter and Sarah’s measures 140. Rachel’s blood glucose level rises slightly, peaking at 30 minutes, measuring approximately 105 milligrams per deciliter. Arthur’s blood glucose decreases, with a low of approximately 85 milligrams per deciliter at 45 minutes.

3. Four individuals measured their baseline blood glucose, then quickly drank a liter of milk. They then measured their blood glucose levels at regular 15-minute intervals for 60 minutes. The results are shown in the graph. Which individual or individuals are lactase persistent, and how do you know?

  1. Arthur, because his glucose level goes down
  2. Rachel, because her glucose level returns to her baseline level.
  3. Peter and Sarah, because their glucose levels increase dramatically after drinking milk.
  4. Peter, Rachel, and Sarah, because their glucose levels went up after drinking milk.

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4. What did researchers discover about genetic mutations that cause lactase persistence?

  1. They are found in the part of DNA that encodes lactase ("the lactase gene").
  2. They are found in a noncoding regulatory region (a "switch") near the lactase gene.
  3. The mutations that cause lactase persistence in European and African populations are identical.
  4. The mutations that cause lactase persistence in European and African populations affect different genes.

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5. Which discovery best supports the hypothesis that evolution of the lactase-persistence trait was driven by dairying, the use of milk as a source of adult nutrition in pastoralist cultures?

  1. Ancient pots used to hold milk are about the same age as the lactase-persistence mutations.
  2. The lactase gene is present in both humans and domesticated animals.
  3. Present-day milk fats and animal body fats can be distinguished using carbon isotope analysis and gas chromatography.
  4. Scientists have discovered different mutations for lactase persistence in different cultures.

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6. How could milk drinking have provided strong favorable selection for lactase persistence? Select all that apply.

  1. Milk could have been a critical food source during times of famine.
  2. Milk is generally safer to drink than water.
  3. Milk is rich in proteins and fats.
  4. Milk could have been given to babies as a source of nutrition.

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7. Suppose that a mutation for lactase persistence occurred in each of the pastoral populations described below. In which population would the mutation be more likely to increase in frequency over time due to natural selection?

  1. A population that raises wheat and sheep.
  2. A population that raises potatoes and chickens.
  3. A population that raises rice and tilapia fish.
  4. A population that raises corn and beans.

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