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Chapter 12 Directed Reading “We’ve found something in the water”
A Plague of Frog
(See Key Below)
Answer the following questions in the space provided. (3 points each)
- What kinds of difficulties were appearing as the autumn of 1997 approached?
- What ended the impasse?
- What is FETAX?
- What did the FETAX results show?
- What does teratogenic mean?
- Why did Judy Helgen decide to “tell everyone” about the results?
- What is the Salk Institute in La Jolla?
- What two essential considerations were the focus of the technical discussions?
- What did this group believe was the only cause of leg malformations?
- What did they think was the disruption?
- What sensational claim did Dave Gardiner make?
- What makes many steroid or vitamin-derived hormones so powerful?
- What is a ligand?
- What does the result of gene expression depend on
- What types of “housekeeping” functions do hormones perform?
- What is an orphan receptor?
- What might some potential practical benefits of this work be?
- What were some of the unanswered questions that remained? Which deformities more common?
- At this point in the investigation, what are the two main hypotheses about the cause of the outbreaks?
- What did Sue Bryant think should be the main focus of the investigation?
- Describe a limitation of the FETAX results.
- What happened with the FETAX results after they were announced to the public
- How does the DNA of a frog compare to that of a human?
- What did Stan Session use regeneration assays for?
- What was the “diffusible morphogen” thought to do?
- What did they speculate was the diffusible morphogen?
- Why did Sue Bryant reject the diffusable morphogen theory?
- What is Rana sylvatica and what did Stan Sessions useit to study?
- How did Sessions know the parasites were trematodes?
- Outline the basics of the parasite theory.
- What is intercalation?
- What was the estimated rate of traumatic amputation Ouellet saw in the field?
- Why did Ouellet think the US investigation was “incompetent”?
Key
Chapter 12 Directed Reading
A Plague of Frogs
Answer the following questions in the space provided. (3 points each)
1.What kinds of difficulties were appearing as the autumn of 1997 approached?
All deformities were being grouped into one category. People started to doubt there was even a problem. Everyone was doing something different and the data did not mesh. Lack
of collaboration. (Page 207)
2. What ended the impasse?
Water testing revealed that a synthetic chemical was found in the water. (Page 208)
3. What is FETAX?
96-hour assay of a water sample using embryos of African Clawed frogs to isolate toxicants. (Page 208)
4. What did the FETAX results show?
Results were positive, producing both high rates of mortality and malformations in lab embryos. Samples were teratogenic. (Page 209)
5. What does teratogenic mean?
Will produce developmental abnormalities. (Page 209)
6. Why did Judy Helgen decide to “tell everyone” about the results?
They were unsure what effects the water would have on other species, including humans. (As a safety precaution.) (Page 209)
7. What is the Salk Instititue in La Jolla?
It is a private research facility that is home to the world’s most prominent hormone receptor lab. (Page 210)
8. What two essential considerations were the focus of the technical discussions?
What would cause a frog to grow malformed limbs?
How would you detect such a causative agent in the environment? (Page 211)
9. What did this group believe was the only cause of leg malformations?
Something disrupting the biochemical signaling necessary for the correct initiation of the limbs. (P.211)
10. What did they think was the disruption?
Retinoids: retinoic acid or a mimic. (Page 212)
11. What sensational claim did Dave Gardiner make?
Pretty soon we would see a person with these deformities. (Page 212)
12. What makes many steroid or vitamin-derived hormones so powerful?
The direct linkage to the DNA. (Page 212)
13. What is a ligand?
The hormone that fits the designated substrate and activates gene expression. (Page 212)
14. What does the result of gene expression depend on?
The hormone and type of cell involved. (Page 212)
15. What types of “housekeeping” functions do hormones perform?
Regulating metabolism. (Page 213)
16. What is an orphan receptor?
A receptor that has been found but whose function is unknown. (Page 213)
17. What might some potential practical benefits of this work be?
Medical breakthroughs as gene therapies are perfected; understanding endocrine disruption. (P.213)
18. What were some of the unanswered questions that remained?
Why were so many deformities unilateral? Why were some deformities more common? (Page 213)
19. At this point in the investigation, what are the two main hypotheses about the cause of the outbreaks?
Chemicals and parasites. (Page 214)
20. What did Sue Bryant think should be the main focus of the investigation?
The retinoid hypothesis. (Page 214)
21. Describe a limitation of the FETAX results.
The actual toxin that caused the deformities was not identified. (Page 215)
22. What happened with the FETAX results after they were announced to the public?
They were retracted although not with a press conference. (Page 216)
23. How does the DNA of a frog compare to that of a human?
It contains more weight than a human’s. (Page 216)
24. What did Stan Session use regeneration assays for?
To measure the effects of genome size on the rate of development. (Page 217)
25. What was the “diffusible morphogen” thought to do?
A master compound that spreads through the developing tissues of limbs and created a concentration gradient. (Page 217)
26. What did they speculate was the diffusible morphogen?
Retinoic acid in limb development. (Page 217)
27. Why did Sue Bryant reject the diffusable morphogen theory?
She was convinced the developing tissues in the limb use cell-to-cell communication. (Page 218)
28. What is Rana sylvatica and what did Stan Sessions useit to study?
The wood frog; to study limb development. (Page 219)
29. How did Sessions know the parasites were trematodes?
He recognized the suckers. Anatomy traits. (Page 220)
30. Outline the basics of the parasite theory.
A definitive host (predator) harbors the mature trematode in its gut. These reproduce and the eggs are excreted in feces dropped in the wetlands and transmitted to aquatic snails. The snail
picks up the egg; the egg hatches and infects the snail. The snail then sheds the larvae into the water. Larvae infect the frogs and create cysts in the limb regions. This makes the frogs more susceptible to
predators (the definitive hosts). Thus, the circle is complete. (Page 221)
31. What is intercalation?
A repair program. A mechanism to reestablish pattern continuity at the cellular level. (Page 228)
32. What was the estimated rate of traumatic amputation Ouellet saw in the field?
Between 1 and 5 percent of the frogs he caught. (Page 232)
33. Why did Ouellet think the US investigation was “incompetent”?
They had not done a comprehensive, random survey across multiple land uses. In other words, they were not studying a large enough sample size. (Page 237)
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