Question

In eukaryotic cell transcription, RNA splicing and RNA capping takes place inside
a. Ribosomes
b. Nucleus
c. Dictyosomes
d. ER

Answer 1

Hint: Transcription is a process of formation of the transcript (RNA) from DNA through the usual process of complementary base pairing, catalyzed and scrutinised by the enzyme RNA polymerase. The genetic information stored in DNA is transcribed into more readable and accessible form in order to produce desired molecules.

Complete answer:
• In eukaryotes, transcription and translation takes place in different cellular compartments: transcription takes place in the nucleus, whereas translation takes place in the cytosol.
• The primary transcript consists of both coding and non-coding regions as a result of which it has to undergo splicing and capping. The coding region is called exons whereas the non-coding region is called introns.
• The primary transcript of an RNA polymerase is referred to as pre-RNA. Processing of eukaryotic pre- RNA involves 5’ capping, 3’ polyadenylation, splicing and RNA editing before being transported to the cytosol, where they are translated by ribosomes.
• The removal of introns from the RNA is called splicing.
• Addition of an unusual nucleotide methyl guanosine triphosphate at the 5' end of hnRNA is called capping.
• Addition of adenylate residue at 3’ end is called tailing.
• The hnRNA which has undergone capping, splicing and tailing now functions as mRNA.
• Ribosomes are involved only after post transcriptional processing is completed. They are involved in translation of the newly formed m-RNA so that the necessary proteins can be constructed.
• Endoplasmic reticulum on the other hand are more involved in the final re-examination and packaging of the prepared proteins whereas dictyosomes are mainly concerned with the storage of protein.

Hence, the correct answer is option (B).

Note: The stretch of DNA transcribed into an RNA molecule is called a transcription unit. The DNA sequences which are expressed or appear in the mature or processed RNA are the exons while those, not appearing in mature or processed RNA are the introns. In prokaryotes, the mRNAs are used in the same compartment as there is no nucleus.