Your friends Ben and Jane are contemplating having children and seek your genetic counsel. Ben and Jane are unrelated, but both have younger brothers with the same, extremely rare genetic trait. (In fact, Ben and Jane met at a support group meeting for children and families of children with this rare disorder.) Ben’s parents and Jane’s parents are all unaffected.        

 Assume that the trait is autosomal dominant with 80% penetrance in heterozygotes and 100% penetrance in homozygotes. What is the probability that Ben and Jane’s first child will be affected? 

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#Question id: 34165

#Unit 7. System Physiology – Animal

Following statements are regarding thyroid hormone biosynthesis?

I. The basolateral membranes of thyrocytes facing the capillaries contain a antiporter that transports two Na⁺ ions and one I^– ion into the cell with each cycle, against the electrochemical gradient for I^–.

II. Na⁺/I^– symporter (NIS) is capable of producing intracellular I^– concentrations that are 20–40 times as great as the concentration in plasma.

III. TSH induces both NIS expression and the retention of NIS in the basolateral membrane, where it can mediate sustained iodide uptake.

TLS Online TPP Program

#Question id: 34166

#Unit 7. System Physiology – Animal

I. Adrenocortical secretion is controlled primarily by ACTH, from the anterior pituitary, but mineralocorticoid secretion is also subject to independent control by circulating factors.

II. Adrenal medullary hormones work mostly to prepare the body for emergencies, the so-called “fight-or-flight” responses.

III. All three cortical zones secrete corticosterone, but the active enzymatic mechanism for aldosterone biosynthesis is not limited to the zona glomerulosa.

IV. An important function of the zona glomerulosa, in addition to aldosterone synthesis, is the formation of new cortical cells.

TLS Online TPP Program

#Question id: 34167

#Unit 7. System Physiology – Animal

I. The adrenal medulla does not regenerate, but when the inner two zones of the cortex are removed, a new ZF and ZR regenerate from glomerular cells attached to the capsule.

II. Immediately after hypophysectomy, the ZF and ZR begin to atrophy, whereas the ZG is unchanged because of the action of angiotensin II on this zone. 

III. The ability to secrete aldosterone and conserve Na+ is normal for some time after hypophysectomy, but in longstanding hypopituitarism, aldosterone deficiency may develop, apparently because of the absence of a pituitary factor that maintains the responsiveness of the zona glomerulosa. 

TLS Online TPP Program

#Question id: 34168

#Unit 7. System Physiology – Animal

Angiotensin II stimulates aldosterone production in the zona glomerulosa by binding to AT1 receptors. Which of the following best describes the intracellular signaling pathway and its role in aldosterone biosynthesis?

TLS Online TPP Program

#Question id: 34169

#Unit 7. System Physiology – Animal

Based on the provided graph panels (A–D), which of the following statements is INCORRECT?

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#Question id: 34170

#Unit 3. Fundamental Processes

What is correct about Klenow fragment

A. is a single polypeptide of 103 kD

B. larger cleavage product of DNA Pol I of 68 kD

C. It contains the polymerase activity

D. It contains the 3’-5’ exonuclease activity

E. It contains the 5’-3’ exonuclease activity