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| 1. |
Degree of antisocial behavior is a quantitative trait in human males. Avshalon Caspi and colleagues (2002) used data on several hundred men to investigate the relationship between antisocial behavior and two factors. The first factor was genotype at the locus that encodes the enzyme monoamine oxidase A (MAOA). MAOA acts in the brain, where it breaks down a variety of the
neurotransmitters nerve cells use to communicate with each other. The gene for MAOA is located on the X chromosome. As a result of genetic differences in the gene’s promoter, some men have low MAOA activity and others have high MAOA activity.The second factor was the experience of maltreatment during childhood. Based on a variety of evidence, the researchers determined whether each man had experienced no maltreatment, probable maltreatment, or severe maltreatment. The data are summarized in Figure 8.30.
- Is the variation among men in antisocial behavior at least partly due to differences in genotype? Explain.
- Is the variation among men in antisocial behavior at least partly due to differences in environment? Explain.
- Do men with different genotypes respond the same way to changes in the environment? Explain.
- Is antisocial behavior heritable? Explain.
- Do these data influence your opinion about how men who exhibit antisocial behavior should be
treated and/or punished?
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 2. |
The serotonin transporter is a cell-surface protein that recycles the neurotransmitter serotonin after it has been used to carry a message between nerve cells in the brain.There are two alleles of the serotonin transporter gene: s and l. Klaus-Peter Lesch and colleagues (1996) found that people with genotypes ls and ss, score slightly, but significantly, higher than people with genotype ll
on psychological tests of neuroticism (see Figure 8.31).
- Are these data consistent with the hypothesis that the serotonin transporter gene is a QTL that influences neuroticism? Explain.
- Is the serotonin transporter gene the gene for neuroticism? Explain.
- Can you think of another plausible explanation, in which the serotonin transporter gene plays no role at all in neuroticism? Explain.
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 3. |
Owners of thoroughbred racehorses might like to know some of the particular loci and alleles that distinguish winners from losers. Describe, in as much detail as possible, a research program that might reveal this information.
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 4. |
Suppose you’re telling your roommate that you learned in biology class that within any given human population, height is highly heritable.Your roommate, who is studying nutrition, says “That doesn’t make any sense, because just a few centuries ago, most people were shorter than they are
now, and it’s clearly because of diet. If most variation in human height is due to genes, how could diet make such a big difference?” Your roommate is obviously correct that poor diet can dramatically affect height. How do you explain this apparent paradox to your roommate?
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 5. |
Now consider heritability in more general terms. Suppose heritability is extremely high for a certain trait in a certain population.There are two important questions:
- First, can the trait be strongly affected by the environment despite the high heritability value? To answer this question, suppose that all the individuals within a certain population have been exposed all their lives to the same level of a critical environmental factor.Will the heritability value reflect the fact that the environment is very important?
- Second, can the heritability value itself change if the environment changes? To answer this question, imagine that the critical environmental factor changes, such that different individuals are now exposed to different levels of this environmental factor. What happens to variation in the trait in the whole population? What happens to the heritability value?
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 6. |
Imagine that a dog breeder has asked you for advice. The breeder keeps Alaskan huskies, which she races in sledding events. She would like to breed huskies that run faster.The table below gives data on the running speeds (m/s) of fifteen families of dogs in the breeder’s kennel.
- Use a piece of graph paper to prepare a scatterplot of midoffspring values versus midparent values. Approximately what is the heritability of running speed in the breeder’s dog population?
- If she selectively breeds her dogs, will the next generation run substantially faster than the dogs she has now?
- What else would you suggest this breeder should try if she wants to win more races?
| Family |
Midparent |
Midoffspring |
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 |
12.7
7.6
14.4
4.3
11.3
12.5
8.9
8.2
6.3
12.7
13.9
7.3
5.9
12.8
12.5 |
10.8
8.0
8.0
9.7
6.6
6.2
12.5
7.4
3.4
6.7
7.9
13.6
7.4
12.1
11.3 |
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 7. |
Imagine that the dog breeder in question 6 were to pick just the five pairs of parents with the highest midparent values, and use them as breeders for the next generation of dogs.
- Calculate the selection differential the breeder has imposed on her population of dogs.
- Use your estimate of the heritability from question 6 and the selection differential you just calculated to predict the average running speed of the dog in the next generation.
- What is the predicted response to selection?
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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| 8. |
In our discussion of Weis and Abrahamson’s work on goldenrod galls (data plotted in Figure 8.24), we mentioned that the researchers established that there is heritable variation among flies in the size of the galls they induce. How do you think Weis and Abrahamson did this? Describe the necessary experiment in as much detail as possible.
[Hint]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
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