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: 12222

#Unit 7. System Physiology – Animal

In acidosis, most of the hydrogen ions secreted by the proximal tubule are associated with which of the following processes?

TLS Online TPP Program

#Question id: 12268

#Unit 7. System Physiology – Animal

 A 40-year-old woman is placed on a high-potassium diet for several weeks. Which of the following hormonal changes is most likely to occur?

TLS Online TPP Program

#Question id: 12269

#Unit 7. System Physiology – Animal

If a woman hears her baby cry, she may experience milk ejection from the nipples even before the baby is placed to the breast. What is the explanation for this?

TLS Online TPP Program

#Question id: 12270

#Unit 7. System Physiology – Animal

Which of the following hormones is not stored in its endocrine-producing gland?

TLS Online TPP Program

#Question id: 12271

#Unit 7. System Physiology – Animal

A young woman comes to the emergency room with a vertebral compression fracture. Radiographs of the spine indicate generalized demineralization. She is vegetarian, does not smoke or drink alcohol, has normal plasma potassium concentration of 5.4 mEq/L, sodium concentration of 136 mEq/L, plasma calcium concentration is 7.0 mg/dL. Her vitamin D3 value is several times greater than normal, although her 1,25-dihydroxycholecalciferol concentration is at the lower limit of detectability. She has been in renal failure for the last 5 years and undergoes hemodialysis three times each week. What is the cause of her low 1,25-dihydroxycholecalciferol level?

TLS Online TPP Program

#Question id: 12272

#Unit 7. System Physiology – Animal

A neonate develops a jaundice condition with a bilirubin concentration of 10 mg/dL on day 2 (normal is 3 mg/dL at 2 days old). The neonatologist can be confident that the condition is not erythroblastosis fetalis if which of the following is true?