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: 14293

#SCPH05 I Biotechnology

#Question id: 14294

#SCPH05 I Biotechnology

#Question id: 14294

#SCPH05 I Biotechnology

#Question id: 14295

#SCPH05 I Biotechnology

Pseudomonas methylotrophus is used to produce single-cell protein from methanol in a 1000 m³ pressure-cycle airlift fermenter. The biomass yield from substrate is 0.41 g g^{- 1}, K_S is 0.7 mg l^{- 1}, and the maximum specific growth rate is 0.44 h^{- 1}. The medium contains 4% (w/v) methanol. A substrate conversion of 98% is desirable. The reactor may be operated either in batch or continuous mode. If operated in batch, an inoculum of 0.01% (w/v) is used and the downtime between batches is 20 h. If operated continuously, a downtime of 25 d is expected per year. Neglecting maintenance requirements, compare the annual biomass production from batch and continuous reactors?

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#Question id: 14296

#SCPH05 I Biotechnology

A two-stage chemostat system is used for production of secondary metabolite. The volume of each reactor is 0.5 m³; the flow rate of feed is 50 l h^{- 1}. Mycelial growth occurs in the first reactor; the second reactor is used for product synthesis. The concentration of substrate in the feed is 10 gl^-1. Kinetic and yield parameters for the organism are:

Assume that product synthesis is negligible in the first reactor and growth is negligible in the second reactor. Determine cell concentrations entering the second reactor.

#Question id: 14297

#SCPH05 I Biotechnology

A two-stage chemostat system is used for production of secondary metabolite. The volume of each reactor is 0.5 m³; the flow rate of feed is 50 l h^{- 1}. Mycelial growth occurs in the first reactor; the second reactor is used for product synthesis. The concentration of substrate in the feed is 10 gl^-1. Kinetic and yield parameters for the organism are:

Assume that product synthesis is negligible in the first reactor and growth is negligible in the second reactor. Determine substrate concentrations entering the second reactor.