Wild type E. coli metabolizes the sugar lactose by expressing the enzyme ß-galactosidase. You have isolated a mutant that you call lac1–, which cannot synthesize ß-galactosidase and cannot grow on lactose (Lac–). During an condition Lac– strain, called lac3–, is linked to the Tn5 insertion. From a strain carrying the Tn5 insertion and lac3– mutation you isolate an F’ that caries a region of the chromosome that includes both Tn5 and the linked Lac region. Introduce this F’ into an F– strain carrying lac1– by selecting for Kanr. These merodiploids express ß-galactosidase normally. What does this result tell you about the relationship between the lac3– and lac1- mutations?  

TLS Online TPP Program

#Question id: 12055

#Unit 7. System Physiology – Animal

Which of the following is a likely consequence of ileal resection?

TLS Online TPP Program

#Question id: 12056

#Unit 7. System Physiology – Animal

A 68-year-old woman with hematemesis has heartburn and stomach pain. Endoscopy shows inflammation involving the gastric body and antrum as well as a small gastric ulcer. Biopsies were positive for Helicobacter pylori. H. pylori damages the gastric mucosa primarily by increasing mucosal levels of which substance?

TLS Online TPP Program

#Question id: 12057

#Unit 7. System Physiology – Animal

A tsunami tidal wave hits the east coast of South America and the people living there are forced to drink unclean water. Within the next several days, a large number of people develop severe diarrhea and about half of these people expire. Samples of drinking water are positive for Vibrio cholerae. Which of the following types of ion channels is most likely to be irreversibly opened in the epithelial cells of the crypts of Lieberkühn in these people with severe diarrhea?

TLS Online TPP Program

#Question id: 12058

#Unit 7. System Physiology – Animal

A 45-year-old man presents with abdominal pain and hematemesis. An abdominal exam was relatively benign, and abdominal x-rays were suggestive of a perforated viscus. Endoscopy revealed a chronically perforated gastric ulcer, through which the liver was visible. Which of the following is a forerunner to gastric ulcer formation?

TLS Online TPP Program

#Question id: 12059

#Unit 7. System Physiology – Animal

A 19-year-old man is fed intravenously for several weeks following a severe automobile accident. The intravenous feeding leads to atrophy of the gastrointestinal mucosa most likely because the blood level of which of the following hormones is reduced?

TLS Online TPP Program

#Question id: 12060

#Unit 7. System Physiology – Animal

 Eating a meal leads to a large increase in gastric acid secretion that peaks within about 5 min and returns to normal about 4 hr after a meal is taken. How long after a meal does the pH of the gastric contents reach its lowest level (in hours)?