You have isolated a set of five yeast mutants that form dark red colonies instead of the usual white colonies of wild-type yeast. You cross each of the mutants to a wild-type haploid strain and obtain the results shown below;

you cross each haploid mutant strain to a different haploid mutant of the opposite mating type. From the results shown below deduce as much as you can about which mutations lie in the same gene. Clearly state any remaining ambiguities and suggest some general ways that the ambiguities might be resolved

a) That mutants 1 and 3 form one complementation group and are mutations in the same gene (gene A) 

b) That mutations 2 and 5 form a second complementation group and are mutations in a second gene (gene B).

c) That mutations 3 and 5 form a second complementation group and are mutations in a second gene (gene B).

d) The first ambiguity is whether mutant 4 has a mutation in gene A or B, or whether it represents a unique gene.

Which of the following is the correct prediction about mutants?

TLS Online TPP Program

#Question id: 34163

#Unit 7. System Physiology – Animal

Which of the following represents the correct sequential pathway for aldosterone synthesis from cholesterol, based on the enzyme-catalyzed steps?

TLS Online TPP Program

#Question id: 34164

#Unit 7. System Physiology – Animal

A newborn is diagnosed with 21β-hydroxylase deficiency. Which of the following downstream consequences is most likely due to impaired glucocorticoid production during fetal life?

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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?