Examine the gene network regulatory motifs in the figure To

Examine the gene network regulatory motifs in the figure. (To recap, (green) lines that end in an arrowhead denote a positive regulator, while (red) lines that end in a crossbar denote a negative regulator). Which network motifs represent negative feedback loops ?

1 A,B and C.

2 D only.

3 B, C and D.

4 A only.

5 None of the regulatory motifs represents a negative feedback loop.

(A) ACTIVATING INPUT (B) ACTIVATING ACTIVATING INPUT INPUT GENE GENE Y GENE GENE GENE ZI GENE Z GENE GENE (D) ACTIVATING INPUT GENEX GENE GEN

Solution

Option 2 is correct.

Negative feedback- The diminuation or counteraction of an effect by its own influence on the process giving rise to it, as when a high level of a particular gene or hormone may inhibit further secretion of that or where the result of a certain action may inhibit further performance of that function.

In A, increase level of gene y inhibit the function of gene x, thats why further reaction is not takes plance.

Same reactions are take place in B and C.

But in D, gene x - gene y - gene -z are formed.

And high level gene z has negative effect on the function of gene x.