You are interested in a new type of autosomal dominant mutation that gives purple eyes in Drosophila. You have a true-breeding purple-eyed line carrying a mutation that you call pr-1. You have isolated a second purple-eyed mutation that you call pr-2, which you have established in a true-breeding line that also carries a recessive marker st, which gives stubby legs. You cross a fly from the pr-1 line to a fly from the st, pr-2 line producing F1 females which you then cross to males from a true breeding st line (normal eyes). From this cross, 1000 progeny flies can be categorized into four different phenotypic classes:

                             

Normally, 3-factor crosses give eight different phenotypic classes, why does this particular cross give only four?

TLS Online TPP Program

#Question id: 12073

#Unit 7. System Physiology – Animal

The figure above shows the concentration of inulin at different points along the renal tubule, expressed as the tubular fluid/plasma ratio of inulin concentration. If inulin is not reabsorbed, what is the approximate percentage of the filtered water that has been reabsorbed prior to the distal convoluted tubule?

TLS Online TPP Program

#Question id: 12074

#Unit 7. System Physiology – Animal

Which of the following tends to increase potassium secretion by the cortical collecting tubule?

TLS Online TPP Program

#Question id: 12075

#Unit 7. System Physiology – Animal

A 48-year-old woman complains of severe polyuria (producing about 0.5 L of urine each hour) and polydipsia (drinking two to three glasses of water every hour). Her urine contains no glucose, and she is placed on overnight water restriction for further evaluation. The next morning, she is weak and confused, her sodium concentration is 160 mEq/L, and her urine osmolarity is 80 mOsm/L. Which of the following is the most likely diagnosis?

TLS Online TPP Program

#Question id: 12076

#Unit 7. System Physiology – Animal

Furosemide (Lasix) is a diuretic that also produces natriuresis. Which of the following is an undesirable side effect of furosemide due to its site of action on the renal tubule?

TLS Online TPP Program

#Question id: 12077

#Unit 7. System Physiology – Animal

 RU486 causes abortion if it is administered before or soon after implantation. What is the specific effect of RU486?

TLS Online TPP Program

#Question id: 12078

#Unit 7. System Physiology – Animal

Following ejaculation, arterial blood flow into the corpora cavernosa decreases back to the normal resting level resulting in the flaccid state. What is the best explanation for this decrease in blood flow?