miRNAs are encoded in the genome as segments of longer transcripts. Their characteristic structure helps identify them and predict the target genes they might regulate. Which of the following are the characteristic features of these small RNA molecules?

I. The functional form of an miRNA is typically 21 or 22 nucleotides (it can vary from 19 to 25 nucleotides).

II. The first cleavage liberates the stem-loop, called the pre-miRNA; the second generates the mature miRNA from the pre-miRNA.

III. The pre-miRNAs can be encoded by any part of a transcript: that is, they might fall within coding regions, within leader regions, or within Introns.

IV. The base pairing between miRNA and target RNA is initiated by interactions of so-called seed residues—the sequence between bases 2 and 9 of the 22-nucleotide miRNA.

#Question id: 12192

#Unit 6. System Physiology – Plant

#Question id: 12191

#Unit 6. System Physiology – Plant

#Question id: 11902

#Unit 6. System Physiology – Plant

A chemiosmotic model  has been proposed  to explain Polar transport , following steps are involve in the transport of auxin polarly;

a) IAA enters the cell either passively in the undissociated form (IAAH) or by secondary active cotransport in the anionic form (IAA–)

b) The cell wall is maintained at an acidic pH by the activity of the plasma membrane H+- ATPase

c) In the cytosol, which has acidic pH, the IAAH form predominates

d) The anions exit the cell via auxin anion efflux carriers that are concentrated at the basal ends of each cell in the longitudinal pathway

Which of the following is the correct statements about the polarly transporting of auxin?

#Question id: 11850

#Unit 6. System Physiology – Plant

The first step in polar transport is auxin influx. According to the model, auxin can enter plant cells from any direction by either of two mechanisms:

a) Passive diffusion of the protonated (IAAH) form across the phospholipid bilayer

b) Secondary active transport of the dissociated (IAA–) form via a 2H+–IAA– symporter

c) Active diffusion of the protonated (IAAH) form across the phospholipid bilayer

Find out the correct statements of about diffusion of IAA.

#Question id: 11849

#Unit 6. System Physiology – Plant

According to chemiosmotic model for polar auxin transport, auxin _____A_______is driven by the______B________ across the plasma membrane, while auxin ___C_____is driven by the_________D_________

#Question id: 11848

#Unit 6. System Physiology – Plant

Polar transport is specific for active auxins, such as