Lactose metabolism in E. coli is carried out by two enzymes, with possible involvement by a third. The genes for all three enzymes are clustered together and transcribed together from one promoter, yielding a polycistronic message. These three genes, linked in function, are therefore also linked in expression. They are turned off and on together.

Negative control	keeps the lac operon repressed in the absence of lactose.
positive control	keeps the operon relatively inactive in the presence of glucose, even when lactose is present.
	when all the glucose is gone and lactose is present, a mechanism should exist.
	is mediated by a factor called catabolite activator protein (CAP), which, in conjunction with cyclic-AMP, stimulates transcription.

#Question id: 11729

#Unit 6. System Physiology – Plant

Given some properties of cytokinin;

a) Kinetin is a naturally occurring plant growth regulator

b) it does occur as a base in the DNA of any species

c) It is a by-product of the heat-induced degradation of DNA

d) the deoxyribose sugar of adenosine is converted to a furfuryl ring and shifted from the 9 position to the 6 position on the adenine ring

which of the following given statements incorrect?

#Question id: 11730

#Unit 6. System Physiology – Plant

Following are some statements regarding plant hormones.

a) Auxin and Cytokinin promote cell division

b) Auxin and Ethylene can cause similar plant responses, such as induction of flowering in pineapple and inhibition of stem elongation

c) cytokinin and ethylene signal transduction pathways are derived from the bacterial two-component regulatory system mainly multistep version

d) Gibberellins Are Synthesized via the terpenoid Pathway

e) GA promotes seed dormancy while ABA causes seed germination

Which of the following from the given above combination is incorrect?

#Question id: 11731

#Unit 6. System Physiology – Plant

Following are some statements regarding the Cytokinin, which of the following is incorrect?

#Question id: 11732

#Unit 6. System Physiology – Plant

Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

a) Induce cell division in callus cells in the presence of an auxin

b) Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

c) promote senescence of leaves

d) Promote expansion of dicot cotyledons

Which one of the following activities are incorrect?

#Question id: 11733

#Unit 6. System Physiology – Plant

The synthetic cytokinin compounds that have not been identified in plants, these are;

#Question id: 11734

#Unit 6. System Physiology – Plant

Some molecules act as cytokinin antagonists, which are able to block the action of cytokinins that is