Q.Describe RNA editing in plants.
🔒You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — RNA Processing and Splicing
A eukaryotic gene's protein-coding sequence is interrupted by non-coding introns (discovered by Roberts and Sharp, 1977 work, 1993 Nobel Prize), while the coding, retained segments are exons. RNA splicing removes the introns from the primary transcript and joins the exons into one continuous coding sequence, carried out inside a large multi-protein machine, the spliceosome (about 40-60 nm across), built from small nuclear ribonucleoprotein particles (snRNPs, combining snRNAs with proteins) that recognise intron boundaries and use a ribozyme to catalyse removal; the mature mRNA then exits the nucleus through a nuclear pore (an energy-dependent process) to reach the ribosomes. Alternative splicing lets one gene generate multiple distinct mature mRNAs, and so multiple protein isoforms, by removing introns (and sometimes even exons) in different combinations from one primary transcript; this expands protein diversity from a fixed gene count, generates multiple related gene products from a single gene, and in plants specifically plays an important role in responding to environmental stress. RNA editing is a further post-transcriptional chemical alteration -- base modification, or nucleotide insertion/deletion -- that changes an mRNA's coding capacity without touching the underlying DNA; in plants it is confined to the mitochondrial and chloroplast (plastid) genomes and coordinates their gene expre …
Plant RNA editing chemically alters mitochondrial and chloroplast mRNA (chiefly C-to-U changes) after transcription, restoring conserved codons and coordinating organelle gene expression. …
Step 1. RNA editing in plants occurs after transcription, chemically altering the transcript by base modification or nucleotide insertion/deletion.
Step 2. It is confined to mitochondria and chloroplasts, coordinating their gene expression with nuclear, environmental and inter-organelle signals.
Step 3. The dominant type is site-specific C-to-U substitution, occurring in both mitochondrial and chloroplast RNA; U-to-C and insertion/deletion editing also occur. …
Define RNA editing, specify where it occurs in plants, describe its dominant chemical form …
- Describing RNA editing as a general eukaryotic process rather than restricting it, in the plant …
- CBSE 2026Set ANNUAL1 markMCQQ.The addition of adenylate residue at the 3' end of a template in an independent manner is called(a) splicing(b) tailing(c) capping(d) split gene
›Reveal solutionSolution
Tailing is the post-transcriptional addition of a poly-A tail to the 3' end of a pre-mRNA, added independently of the DNA template.
Among the post-transcriptional processing steps of eukaryotic hnRNA (heterogeneous nuclear RNA, the primary transcript), 'tailing' refers specifically to the addition of about 200–300 adenylate (adenine nucleotide) residues at its 3' end, forming a poly-A tail. Unlike normal transcription, this addition occurs independently of the DNA template. Splicing (a) is the removal of introns and joining of exons, capping (c) is the addition of a …
- CBSE 2026Set ANNUAL1 markQ.What is splicing?
›Reveal solutionSolution
Splicing edits out the non-coding intron sequences of a pre-mRNA and stitches the coding exons together to make mature mRNA.
In eukaryotes, genes are typically 'split genes', composed of alternating coding sequences (exons) and non-coding sequences (introns). The primary transcript (hnRNA) produced by transcription contains both exons and introns. Splicing is the process, occurring within the nucleus, by which the intervening intron sequences are precisely removed and the exon sequences are joined together, producing the final, mature mRNA m …
- CBSE 2026Set ANNUAL1 markMCQQ.Removal of introns and joining of exons in a defined order during transcription is called :(a) Inducing(b) Splicing(c) Slicing(d) Looping
›Reveal solutionSolution
The removal of introns and the joining of exons in a defined order, during processing of the RNA transcript, is called splicing.
Working
In eukaryotes, the RNA polymerase first produces a primary transcript (pre-mRNA or hnRNA) that contains both coding regions (exons) and intervening non-coding regions (introns), copied directly from the gene. Before this transcript can serve as a template for translation, it must be processed: the intron sequences are precisely excised, and the remaining exon sequences are joined together end to end, in their original, defined order, to produce the shorter, mature mRNA. This excision-and-joining process is called splicing, and it is carried out inside the nucleus by a large ribonucleoprotein machine called the spliceosome, which recognises specific sequence signals at each intron-exon boundary. Splicing is essential because if the i …
- CBSE 2024Set ANNUAL1 markMCQQ.Removal of introns and joining of exons in a defined order during transcription is called :(a) Inducing(b) Splicing(c) Slicing(d) Looping
›Reveal solutionSolution
The removal of introns and joining of exons in a defined order during mRNA processing is called splicing, carried out by the spliceosome.
Working
The primary transcript produced by RNA polymerase II (hnRNA/pre-mRNA) in eukaryotes contains alternating coding sequences (exons) and non-coding intervening sequences (introns). Before the transcript can be translated, it must be processed: the introns are precisely excised, and the exons are spliced (joined) together in the correct, defined order to produce the mature mRNA. This process, called splicing, is carried out by a large ribonucleoprotein complex called the spliceosome, which recognises specific sequences at intron-exon boundaries. It is essential because untranslated intron sequences …
- CBSE 2020Set NC1 markMCQQ.DNA sequences that code for protein are known as(a) introns(b) exons(c) control regions(d) intervening sequences
›Reveal solutionSolution
Eukaryotic genes are typically "split," containing alternating coding and non-coding stretches; only the coding stretches — exons — are retained in the mature mRNA after splicing and are ultimately translated into protein.
Reasoning
Many eukaryotic genes are interrupted, containing both coding sequences (exons, which are Expressed and retained in the mature mRNA) and intervening, non-coding sequences (introns, which are Intervening and are removed/spliced out before translation). After the primary RNA transcript (hnRNA) undergoes RNA splicing, the introns are excised and the remaining exons are joined together t …
- CBSE 2018Set ANNUAL1 markMCQQ.Expressed sequences in the gene are called(a) Introns(b) Mutons(c) Exons(d) Cistrons
›Reveal solutionSolution
In a split (eukaryotic) gene, the coding/expressed sequences that appear in mature mRNA are called exons; the non-coding sequences that are removed are called introns.
Most eukaryotic genes are 'split genes' — their coding sequence is interrupted by non-coding stretches.
- Exons are the sequences that appear/are expressed in the mature, processed mRNA. They contain the actual coding information used for translation.
- Introns (intervening sequences) are the non-coding stretches that interrupt the coding sequence; they are transcribed into the primary (hnRNA) transcript but are removed during RNA splicing before the mRNA leaves the nucleus.
- Splicing is the process by which introns are cut out and exons are joined together to form the mature, translatable mRNA. …
🎓Unlock everything free for 14 days
- ✓Full step-by-step solutions
- ✓Concept-first explanations
- ✓Methods, shortcuts & mistakes
- ✓PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.