Exons are nucleotide sequences that carry information for protein synthesis, whereas introns are interrupting sequences that do not code for any protein but are found between exons. Prokaryotes have a single circular, double-stranded DNA in nucleoid form (the central part of the cell). Noncoding regions are not present in their DNA because they have small DNA. Large linear DNA is found in eukaryotes as compactly packed chromatin. Because eukaryotic DNA contains coding and noncoding regions, known as hnRNA, contains exons and introns. Because the introns are removed during the hnRNA-to-mRNA conversion process, the mature mRNA contains only exons.
Exons and Introns Meaning
Now in this article we will understand what Exons and Introns are.
What are introns?
Introns are non-coding DNA sequences within a gene that are removed during RNA splicing during RNA product maturation.The term ‘intron’ refers to the intragenic region found within a gene.The term ‘introns’ refers to both the DNA sequences within the gene and the corresponding RNA transcript sequence.
Introns can be found in the genes of many eukaryotic organisms as well as some viruses. They can be found in most genes, including those that produce proteins, ribosomal RNA (rRNA), and transfer RNA (tRNA). These, however, do not exist in prokaryotes.
Introns are common in most jawed invertebrates’ protein-coding nuclear genes, but they may be uncommon in some eukaryotic organisms.
Similarly, the mitochondrial genomes of jawed vertebrates are almost entirely devoid of introns, whereas those of other eukaryotes are densely packed with them.
RNA splicing occurs as a process of RNA processing that occurs after transcription and before translation during the generation of proteins from genes containing introns.
The function of intron
The intron architecture of many eukaryotic genes begs the question of whether this unusual organisation serves any purpose, or if it is simply a result of the proliferation of functionless introns in eukaryotic genomes. In this review, we show that introns in modern species serve a wide range of functions and are involved in nearly every step of mRNA processing. We propose that the wide range of intronic functions supports the idea that introns were initially selfish elements in early eukaryotes, but then independently acquired a wide range of functions in different eukaryotic lineages. We propose a new evolutionary conservation criterion, intron positional conservation, that can identify functional introns.
The past and future of introns
The existence of introns and differential splicing contributes to our understanding of how new genes are created during evolution. Splicing makes genes more “modular,” allowing for the creation of new exon combinations during evolution. Furthermore, new exons can be inserted into old introns, resulting in the production of new proteins without interfering with the function of the old gene.
Our understanding of RNA splicing is relatively new. Nonetheless, because nearly all eukaryotes have introns and share RNA splicing mechanisms, splicing must be quite ancient. Proponents of the “intron-early” theory believe that all organisms (including prokaryotes) once had introns in their genomes but lost them, whereas supporters of the “intron-late” theory believe that the restriction of introns to eukaryotes indicates a more recent introduction (Roy & Gilbert, 2006).
What are Exons?
Exons are DNA sequences that contain protein-coding information and require the necessary codons or information for protein synthesis.The term exons refers to the expressed region of the genome.In eukaryotes, genes are made up of coding exons separated by non-coding introns.
The introns between the exons are removed during RNA splicing to connect two different introns that then code for messenger RNA.
Exosome refers to the entire set of all exons found in an organism’s genome.
Exons in protein-coding genes contain both the protein-coding sequence and the 5′ and 3′ untranslated regions.
The resulting RNA contains both exons and introns after these genes are transcribed. RNA splicing then removes the introns, resulting in mature mRNAs.
Exons and untranslated regions are thus present in mature mRNA transcripts, with exons constituting a small portion of the entire sequence.Exons can be found in all organisms, from jawed vertebrates to viruses.
What is RNA splicing?
RNA splicing is the process of converting pre-mRNA into mature mRNA by removing introns and joining exons together. Splicing methods vary depending on the organism, the type of RNA or intron structure, and the presence of catalysts.
Introns have a highly conserved GU sequence at the 5′ end known as the donor site and a highly conserved AG sequence at the 3′ end known as the acceptor site. The spliceosome, a large RNA-protein complex composed of five small nuclear ribonucleoproteins (snRNPs), recognises the start and end points of the intron using these sites and catalyses the removal of the intron accordingly. The spliceosome converts the intron into a cleavable loop, and the remaining RNA on the intron is cleaved.
Conclusion
Exons are nucleotide sequences that carry information for protein synthesis, whereas introns are interrupting sequences that do not code for any protein but are found between exons. Because the introns are removed during the hnRNA-to-mRNA conversion process, the mature mRNA contains only exons. Introns are non-coding DNA sequences within a gene that are removed during RNA splicing during RNA product maturation. The term ‘introns’ refers to both the DNA sequences within the gene and the corresponding RNA transcript sequence. RNA splicing occurs as a process of RNA processing that occurs after transcription and before translation during the generation of proteins from genes containing introns.