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Question
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
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Solution
Nucleic acid polymerases are of the following types –
- DNA polymerase: This enzyme is essential for replication. It uses DNA template to induce polymerisation of deoxynucleotide. Both chains of DNA molecules do not separate together. DNA double helix opens in small parts for replication. The resulting parts are joined with each other by DNA ligase enzyme. DNA polymerase cannot initiate the replication process on its own. It happens with the help of vector at certain sites.
- RNA polymerase: This is DNA dependent RNA polymerase. It catalyses DNA for transcription of all types of RNA. RNA polymerase temporarily binds with initiation factor or termination factor and initiates or terminates transcription. Apart from DNA dependent RNA polymerase, the following three types of RNA polymerases are found in the nucleus –
- RNA Polymerase I: It transcribes ribosomal RNA (r-RNA).
- RNA Polymerase II: It transcribes heterogeneous nuclear RNA (hnRNA), the precursor of messenger RNA (m-RNA).
- RNA Polymerase III: It is responsible for the transcription of transfer RNA (t-RNA) and small nuclear RNA.
RELATED QUESTIONS
Explain the process of making heterogeneous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this process occur in the cell?
Answer the following question.
Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA.
With regard to mature mRNA in eukaryotes.
Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein?
Methyl guanosine triphosphate is added at 5' end of hn-RNA in a process of ______.
If the base sequence of a codon in mRNA is 5'-AUG-3', the sequence of tRNA pairing with it must be ______.
To initiate translation, the mRNA first binds to ______.
In transcription in eukaryotes, heterogeneous nuclear RNA (hnRNA) is transcribed by ______.
A special feature of viruses is that they:
Ribozyme is a/an:
The most likely method, used to determine the structural details of the cell organelle is ______.
Sigma factor is a component of ______.
Refer the given diagram. What does it represent?
Identify the correct statement.
Which is the “Only enzyme” that has “Capability” to catalyse Initiation, Elongation and Termination in the process of transcription in prokaryotes?
What are the functions of methylated guanasine cap?
What are the functions of poly-A “tail” in a mature on RNA?
Give an account of post transcriptional modifications of a eukaryotic mRNA.
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 a polypeptide, stating the reasons.
- Assertion: Ribosomal RNA is synthesized in the nucleus of the cell.
- Reason: It is translated with the enzyme RNA polymerase III.
