Observe the segment of mRNA given below.
(a) Explain and illustrate the steps involved to make fully processed hnRNA?
(b) Gene encoding RNA Polymerase I and III have been affected by mutation in a cell. Explain its impact on the synthesis of polypeptide, stating reasons.
Answer:
(a) The hnRNA undergoes processes called capping and tailing followed by splicing .In capping, an unusual nucleotide is added to the 5¢-end of hnRNA methyl guanosine triphosphate.In tailing, adenylate residues (about 200–300) are added at 3¢-end in a template independent manner.Now the hnRNA undergoes a process where the introns are removed and exons are joined to form mRNA called splicing.
(b) The process of translation will not happen, thus the polypeptide synthesis is stopped/ hampered.
The reason for the above is:
RNA polymerase I transcribes rRNAs which is the cellular factory for protein synthesis.
RNA polymerase III helps in transcription of tRNA which is the adaptor molecule/ that transfers amino acids to the site of protein synthesis.
