Question

Which of the following is not true of RNA processing?

• A. Exons are excised and hydrolysed before mRNA moves out of the nucleus.
• B. An initial RNA transcript is much longer than the final RNA molecule that may leave the nucleus.
• C. RNA splicing may be catalyzed by spliceosomes.
• D. RNA splicing only takes place in eukaryotic nucleus.

Answer 1

The correct option is A Exons are excised and hydrolysed before mRNA moves out of the nucleus.

• In most eukaryotic genes, coding regions (exons) are interrupted by noncoding regions (introns).
• During transcription, the entire gene is copied into a pre-mRNA, which includes exons and introns.
• During the process of RNA splicing, introns are excised and hydrolyzed before mRNA moves out of the nucleus, and exons are joined to form a continuous coding sequence.
• Hence, an initial RNA transcript is much longer than the final RNA molecule that may leave the nucleus.
  
• The spliceosome, a large RNA-protein complex catalyzes splicing.
  
• Introns are absent in the DNA of prokaryotes, so there is no need for RNA splicing.

So, the correct option is 'Exons are excised and hydrolysed before mRNA moves out of the nucleus'.