Shortly after the discovery of kinetin, it was observed that the differentiation of cultured callus tissue derived from tobacco pith segments into either roots or shoots depends on the ratio of auxin to cytokinin in the culture medium. Whereas

a) high auxin:cytokinin ratios stimulated the formation of roots

b) high auxin:cytokinin ratios stimulated the formation of shoots

c) low auxin:cytokinin ratios led to the formation of shoots

d) low auxin:cytokinin ratios stimulated the formation of roots

which of the following combination is correct about the ratio of auxin to cytokinin

TLS Online TPP Program

#Question id: 34145

#Unit 7. System Physiology – Animal

I. The short arm of human chromosome 17 contains the growth hormone-hCS cluster.

II. Growth hormone increases circulating IGF-I, which in turn exerts a direct inhibitory action on growth hormone secretion from the pituitary.

III. Growth hormone secretion is decreased in persons deprived of rapid eye movement (REM) sleep.

IV. Growth hormone secretion is induced by thyroid hormones & inhibited, by cortisol.

TLS Online TPP Program

#Question id: 34146

#Unit 7. System Physiology – Animal

I. Human pituitary prolactin has considerable structural similarity to human growth hormone and human chorionic somatomammotropin (hCS).

II. Structurally similar prolactin are secreted by the endometrium and by the placenta.

III. prolactin secretion is increased during pregnancy, reaching a peak at the time of parturition.

IV. The human prolactin receptor resembles the oxytocin receptor.

TLS Online TPP Program

#Question id: 34147

#Unit 7. System Physiology – Animal

Which of the following statements not CORRECT regarding the mechanism and reproductive role of prolactin during lactation?

TLS Online TPP Program

#Question id: 34148

#Unit 7. System Physiology – Animal

Assertion (A): Prolactin stimulates the synthesis of casein and lactalbumin during lactation without acting directly on the cell nucleus.

Reason (R): The action of prolactin is dependent on intact microtubules, suggesting involvement of cytoplasmic transport or signaling components.

Choose the correct option:

TLS Online TPP Program

#Question id: 34149

#Unit 7. System Physiology – Animal

A scientist finds that infusion of growth hormone into the median eminence of the hypothalamus in experimental animals inhibits the secretion of growth hormone and concludes that this proves that growth hormone feeds back to inhibit GHRH secretion. Do you accept this conclusion?

TLS Online TPP Program

#Question id: 34150

#Unit 7. System Physiology – Animal

A 7-year-old boy is evaluated for short stature. His average circulating growth hormone level is within the normal range for his age, but levels of IGF-I are reduced. His growth failure is most likely due to a defect in: