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Difference Between Introns and Exons – Introns vs Exons

Introns are non-coding DNA DNA sequences in a gene. They are removed through RNA splicing during maturation of the product of RNA.

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MN Editors

What is Introns?

Introns are non-coding DNA DNA sequences in a gene. They are removed through RNA splicing during maturation of the product of RNA.

Introns are the intragenic region located in the gene. Introns refer to that the sequence of DNA in the gene and the associated sequence of transcripts of RNA. Introns are present in the genes of many eukaryotic species and viruses. They can be found in many genes, including those that produce proteins, ribosomalRNA (rRNA) and transfer transcript RNA (tRNA). However, they are not present in prokaryotes. Introns are found in nuclear proteins that code for protein of jawed invertebrates. However, they are not common in some eukaryotic organisms.

The DNA of jawed vertebrates’ mitochondrial genomes are nearly completely devoid of introns, whereas the genomes of other eukaryotes include numerous introns. When proteins are made that are derived from genes with introns the splicing of RNA is the process of processing RNA that occurs following transcription but before the translation. There are several types of introns according to their sequence analysis, as well as the biochemical and genetic analysis of RNA splicing strategies.

The four most popular types of introns comprise;

  • Spliceosome introns on nuclear protein-coding genes are eliminated by Spliceosomes
  • TRNA introns within archaeal and nuclear tRNA gene which are eliminated by proteins
  • self-splicing introns of group I removed through catalytic RNA synthesis
  • self-splicing group II introns eliminated through catalytic RNA removal

Introns from different species are also eliminated and acquired throughout evolution as seen in various Eukaryotes. Introns are vital since the proteins are significantly increased by alternative splicing, whereintrons play a role of important functions. Alternative splicing is controlled molecular process that produces many different proteins from one gene within a eukaryotic cell. The rate of expression is significantly enhanced in when introns are present. It is also known that spliced transcripts move more quickly from the nucleus to the cytoplasm than those that are not spliced. But, the presence of introns within the genome may cause problems for some cells because they require a large amount of energy in order to copy and expel them precisely in the proper places using complex spliceosomal procedures.

What is Exons?

Exons are DNA sequences that encode proteins which require codons or other information needed to make proteins.

The term “exon” refers to the expressible region that exists within the genome. The genes of eukaryotes comprised of coding exons, divided by introns that are not coding. In RNA splicing, introns in between the exons get removed in order to link two different introns, which then encode messages RNA. The complete set of exons within the genomes of organisms is known as the exosome. For genes that encode proteins, exons comprise both the protein-coding sequence , as well as the 5 3′ and ‘untranslated’ regions. When these genes are transscribed and transcribed, the resulting RNA contains both introns and exons. Introns are removed through RNA splicing. This results in mature MRNAs.

The mature transcripts of mRNA contain exons as well as untranslated regions where exons constitute just a small portion of the whole sequence. Exons can be found in every living things from jawed vertebrates up to viruses. The human genome is only 1% of our genome’s total is comprised of exons whereas the rest is comprised of intergenic DNA and introns. Sometimes, introns can be transformed into exons through exonization. Exons are vital to protein synthesis because they contain codons that encode for different proteins.

In the presence of exons as well as introns allows for alternative splicing which expands the number of proteins that can be produced from one gene. Alternative splicing permits exons to be placed in various sequences and produce various proteins. Another process that is like alternative splicing is shuffling exons in which exons or sister chromosomes can be swapped during the process of recombination. Alternative splicing can be found in a human gene which is a transmembrane proteins that regulates potassium entry into hair cells. The gene is comprised of 35 exons that can be combined in various ways or forms to create more than 500 mRNAs through the reshuffling of 1-8 exons.

Difference Between Introns and Exons – Introns vs Exons

Base for comparisonIntronsExons
DefinitionIntrons are non-coding DNA DNA sequences inside a gene. They’re eliminated by RNA splicing in the maturation of the RNA.Exons are DNA sequences that encode proteins that require codons or the information required to make proteins.
Sequence typeIntrons are non-coding sequences which do not encode for any protein.Exons are proteins-coding sequences which encode specific proteins.
Location in the DNAIntrons can be found between exons within the DNA sequence.Exons are sequences that encode for proteins which are located between the untranslated regions or the two introns.
DistributionThey are only found in genomes that are eukaryotic.They can be found in both prokaryotic and eukaryotic genomes.
The cell’s location is within the cellIntrons are retained in the nucleus even after they have been deleted from the mRNA transcript in the process of RNA processing.Exons are released from the nucleus to be released into the cytoplasm once the mature mRNAs have been synthesized.
Present inIntrons are found in DNA and mRNA transcripts however they are not found in mature mRNAs.Exons can be found on DNA transcripts, in mRNA transcripts and mature transcripts of RNA.
ConservedIntron sequences are as stable like the sequences in exons. Introns may convert to exons through this process called exonization.Exon sequences are extremely conserved.
InvolvedIntrons do not play a role in the process of protein synthesis.Exons play a role in the synthesis of proteins.
QuantityIntrons are more abundant within the genome of nuclear cells than exons.Exons are less abundant in amount than introns within the nucleus genome.
Human genomeAbout 24% of human genome is comprised of introns.Just 1% of human DNA is made up of exons.
Alternative splicingIntrons are eliminated by alternative splicing.Exons with two or more can be connected by different splicing.
Novel genes formationIntrons could result in the creation of new genes, as the non-coding regions could develop into functional genes by way of continual evolution.Exons can be combined in a different way, resulting in various sequences that code for various proteins.



MN Editors. (January 16, 2022).Difference Between Introns and Exons – Introns vs Exons. Retrieved from https://microbiologynote.com/difference-between-introns-and-exons/


MN Editors. "Difference Between Introns and Exons – Introns vs Exons." Microbiology Note, Microbiologynote.com, January 16, 2022.


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