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प्रश्न
Explain the processing the hnRNA needs to undergo before becoming functional mRNA in eukaryotes.
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उत्तर
In eukaryotes, the hnRNA (heterogeneous nuclear RNA) is the direct product of transcription and contains both coding exons and non-coding introns. To become functional mRNA, it must undergo three essential processing steps within the nucleus:
- Splicing: This is the most critical step, where the non-functional introns are removed, and the functional exons are joined together in a specific order. This process is carried out by a complex called the spliceosome.
- Capping: A unique nucleotide, methyl guanosine triphosphate, is added to the 5’ end of the hnRNA. This “cap” protects the RNA from degradation and helps the ribosome recognise it during translation.
- Tailing (Polyadenylation): About 200–300 adenylate residues are added to the 3’ end of the RNA, forming what is known as a poly-A tail. This tail assists in the export of the mRNA from the nucleus and further stabilises the molecule.
Once these three modifications are complete, the processed transcript is called mature mRNA and is then transported out of the nucleus into the cytoplasm for protein synthesis.
संबंधित प्रश्न
Following are the features of genetic codes. What does each one indicate?
Stop codon; Unambiguous codon; Degenerate codon; Universal codon.
Describe the process of transcription in bacteria
- Name the scientist who suggested that the genetic code should be made of a combination of three nucleotides.
- Explain the basis on which he arrived at this conclusion.
Name the enzyme responsible for the transcription of tRNA and the amino acid the initiator tRNA gets linked with.
How is Prokaryotic Transcription process different in eukaryotes?
Explain the mechanism of transcription in a prokaryotic cell.
Which of the following is the correct sequence of event with reference to the central dogma?
Name the parts marked ‘A’ and ‘B’ in the given transcription unit:
DNA template sequence of CTGATAGC is transcribed over mRNA as ______.
The process of copying genetic information from one strand of DNA to RNA is termed as ______.
Read the following and answer from given below:
The translation is the process of polymerization of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence bases in the mRNA. The amino acids are joined by a bond called a peptide bond. The ribosome is the site of protein synthesis.
Which ion is essential for the association of both units of the ribosome at the time of protein formation?
Match List I with List II.
| List I | List II |
| A. RNA polymerase III | I. snRNPs |
| B. Termination of transcription | II. Promotor |
| C. Splicing of Exons | III. Rho factor |
| D. TATA box | IV. SnRNAs, tRNA |
Choose the correct answer from the options given below:
Which enzyme is responsible for catalyzing the transcription process?
In eukaryotes, where does transcription occur?
What is the direction of the coding strand?
Which part of a transcription unit serves as the stop site for transcription?
How many stages does transcription occur in?
What happens during the termination stage of transcription?
In eukaryotes, what is the name of the primary RNA product immediately after transcription?
