Transcription of eukaryotic genes can be repressed in various ways. These include the four mechanisms

1. Competition	a-Repression is caused by recruiting histone modifiers that alter nucleosomes in ways that inhibit transcript
2. Inhibition	b-A repressor binds to a site on DNA beside an activator and interacts with that activator, occluding its activating region
3. Direct repression	c-By binding to a site on DNA that overlaps the binding site of an activator, a repressor can inhibit binding of the activator to a gene and thus block activation of that gene.
4. Indirect repression	d-A repressor binds to a site upstream of a gene and, by interacting with the transcriptional machinery at the promoter in some specific way, inhibits transcription initiation.

TLS Online TPP Program

#Question id: 34160

#Unit 7. System Physiology – Animal

The causes of ACTH-independent Cushing syndrome include following, EXCEPT? 

TLS Online TPP Program

#Question id: 34161

#Unit 7. System Physiology – Animal

Congenital defects in the enzymes lead to deficient cortisol secretion and the syndrome of congenital adrenal hyperplasia. A cause of severe congenital adrenal hyperplasia in newborns is a loss of function mutation of the gene for the: 

TLS Online TPP Program

#Question id: 34162

#Unit 7. System Physiology – Animal

Gonadal and adrenocortical steroids are of following types, EXCEPT? 

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?

TLS Online TPP Program

#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.