Meselson and Stahlʹs experiments involved growing E. coli on a medium containing 15N (heavy nitrogen) which increased the density of the bacterial DNA. Cells were then grown on a medium containing only 14N. DNA samples were obtained for analysis after one, two and three rounds of replication (generations) and centrifuged on a density gradient. The double-helical DNA forms bands in the gradient depending on its density. How many bands did Meselson and Stahl see after two generation of cells were grown on the 14N medium?

#Question id: 10339

#Unit 6. System Physiology – Plant

Nitrate assimilates into the root where the conversion of nitrate to nitrite in the cytosol, a reduction reaction that involves the transfer of two electrons catalyzes by an enzyme that is NAD(P)H dependent is known as

#Question id: 10340

#Unit 6. System Physiology – Plant

There several charecteristics of nitrate reductase, which of the following properties of nitrate reductase is incorrect?

#Question id: 10341

#Unit 6. System Physiology – Plant

The accumulation of nitrate that results from diminished nitrate reductase activity, this symptoms is caused by

#Question id: 10342

#Unit 6. System Physiology – Plant

Nitrate reductase is an important enzyme for nitrate assimilation. Given below some regulation of nitrate reductase activity through phosphorylation and dephosphorylation.

a) Light, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby activates the enzyme

b) In Dark, and Mg2+ stimulate a protein kinase that phosphorylates the same serine residues, which then interact with a 14-3-3 inhibitor protein, and thereby inactivate nitrate reductase

c) In Light, and Mg2+ stimulate a protein kinase that phosphorylates the serine residues, and thereby activate nitrate reductase

d) In Dark, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby inactivates the enzyme

Which of the following statements about regulation of nitrate reductase is correct?

#Question id: 10343

#Unit 6. System Physiology – Plant

In many plants, nitrate is assimilated in the root as well as in the shoot according to their native place. Some of the given statements about nitrate assimilation;

a) If plants native to temperate region assimilate NO3^- at root

b) If plants native to temperate region assimilate NO3^- at shoot

c) Plants native to tropical or subtropical region assimilate NO3^- at root

d) Plants native to tropical or subtropical region assimilate NO3^- at shoot

Which of the following combination from above statements is correct?

#Question id: 10344

#Unit 6. System Physiology – Plant

Some of the following caracteristics of Nitrite reductase, which one of the is incorrect?