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Question: hnRNA undergoes two additional processes. In one of the processes, an unusual nucleotide (methyl GPT...

hnRNA undergoes two additional processes. In one of the processes, an unusual nucleotide (methyl GPT) is added to the 5’ end of the molecule. What would you call this?
A. Tailing.
B. Splicing.
C. Termination.
D. Capping.

Explanation

Solution

hnRNA is present generally outside the nucleolus of the cell. It is made up of pre mRNA which after processing becomes the mature mRNA through various modifications. These modifications are 5' modification, 3' polyadenylation, and RNA splicing, that occur inside the nucleus of the cells before the process of translation.

Complete answer:
-Tailing- is the process of addition of the chain of adenine nucleotides i.e., called as poly A tail or tailing process, at the 3’ end of the hnRNA and this process is known as tailing mechanism. The primary function of the tailing is to protect the mRNA by nuclease action.
-Splicing- Introns are always eliminated from hnRNA by the procedure called splicing. It is done for the formation of functional mRNAs that consist of only the exon parts of the RNA. Thus, various different mRNAs can be obtained by a single hnRNA primary transcript by the procedure of splicing.
-Termination- RNA polymerase helps in transcription of mRNA until it gets signals to stop transcribing. This way of ending transcription is known as termination, and it always occurs once the polymerase comes transcribing a sequence called as a terminator, where it stops.
-Capping- is the process of addition of the methyl GPT at the 5’ end of the hnRNA and this process is known as capping. Guanylyl transferase is the enzyme that is used in this process of capping. Capping is a very important process for the formation of mRNA- ribosome complexes. If there is no capping then, there is no translation because it is the capping that is identified by sRNA of ribosomes.

Hence, the correct answer is option (D).

Note: The 5′ capping saves the developing mRNA from deterioration and helps in binding of the ribosome in the process of translation. The poly (A) tail saves the mRNA from degradation, helps in the transferring of the mature mRNA to the cell’s cytoplasm region, also helps or is involved in binding proteins during initiating translation.