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TLS Online TPP Program

#Question id: 799

The two cleavage reactions required to generate the miRNA from these primary transcripts are mediated by two distinct RNases. A characteristic of both these enzymes is that they recognize and cleave RNAs on the basis of the structure of their substrates rather than their specific sequence. Which of the following statement is INCORRECT regarding the cleavage reactions that produces a mature RNA?

#Unit 1. Molecules and their Interaction Relevant to Biology

  1. Drosha resides in the cell’s nucleus, and the Drosha-catalyzed cleavage event occurs in that cellular compartment that generates a pre-miRNA which is ~65–70 nucleotides long.

  2. The pre-miRNA liberated by Drosha is exported to the cytoplasm, where the second RNA cleavage reaction, performed by Dicer, takes place which cleaves pre-miRNA 22 nucleotides from its ends.

  3. For processing by Drosha, ssRNA lacking significant secondary structure, is needed flanking each side (5’ and 3’) of the stem-loop. It is the ssRNA–dsRNA junctions that are in responsible for determining the cleavage specificity of Drosha.

  4. The RNase II family enzymes are specific for dsRNA and cleave it in a manner that leaves a 2-nucleotide overhang on the 3’ ends of the dsRNA product. This 3’ overhang is important for recognition of that RNA molecule by the next enzyme in the pathway, Dicer.

More Questions
TLS Online TPP Program

#Question id: 4111

#Unit 3. Fundamental Processes

Which of the following is NOT characteristic of a eukaryotic enhancer element?
TLS Online TPP Program

#Question id: 4112

#Unit 3. Fundamental Processes

Which of the following is the structure of the nucleotide at the branch site of a spliced intron?
TLS Online TPP Program

#Question id: 4113

#Unit 3. Fundamental Processes

Match the transcriptional machinery with their respective RNA Polymerase
TLS Online TPP Program

#Question id: 4114

#Unit 3. Fundamental Processes

Splice-site recognition is prone to two kinds of errors. First, splice sites can be skipped, with components bound at, for example, a given 5’ splice site pairing with those at a 3’ site beyond the correct one. Ways in which the accuracy of splice-site selection can be enhanced are as

A. The factors that recognize that site are transferred from the polymerase carboxy-terminal “tail” onto the RNA. Once in place, the 5’ splice site components are poised to interact with those other factors that bind to the next 3’ splice site to be synthesized.

B. SR (serine–arginine-rich) proteins bind to sequences called exonic splicing enhancers (ESEs) within the exons. SR proteins bound to these sites recruit the splicing machinery to the nearby splice sites to ensure correct splicing

C. By recruiting splicing factors to each side of a given exon, this process encourages the so-called “exon definition, contribute to correct splicing

D. Alternative splicing is intentional missplicing mechanism

Which of the following is INCORRECT?
TLS Online TPP Program

#Question id: 4115

#Unit 3. Fundamental Processes

The possible type of splicing outcome of given gene construct will be
TLS Online TPP Program

#Question id: 4116

#Unit 3. Fundamental Processes

Proteins that regulate splicing bind to specific sites called exonic (or intronic) splicing enhancers (ESE or ISE) or silencers (ESS and ISS). The former enhances, and the latter repress, splicing at nearby splice sites. Examples of splicing activator and repressors are as