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'''Exon''' is a term in genetics that refers to a sequence of DNA or RNA which codes information for protein synthesis. In other words, exons are the portions of a gene that are expressed (i.e., translated into a protein). They are interspersed with non-coding sequences, known as [[introns]], which are removed during the process of [[RNA splicing]].
{{Short description|Detailed overview of exons in genetics}}


== Overview ==
==Overview==
An '''exon''' is a segment of a [[DNA]] or [[RNA]] molecule containing information coding for a protein or peptide sequence. In the context of [[gene expression]], exons are the portions of a [[gene]] that are transcribed into [[messenger RNA]] (mRNA) and are retained after the [[RNA splicing]] process. Exons are crucial for the synthesis of proteins, as they provide the necessary coding sequences that are translated into the amino acid sequences of proteins.


The term "exon" was first coined in 1978 by American biochemist [[Walter Gilbert]] to refer to both the expressed region of a DNA sequence within a gene and the corresponding sequence in RNA molecules. The definition of an exon remains a matter of debate among scientists, but it is generally accepted that an exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule.
==Structure and Function==
Exons are interspersed with non-coding sequences known as [[introns]]. During the process of [[transcription]], both exons and introns are initially copied into a precursor mRNA (pre-mRNA) molecule. However, before the mRNA can be translated into a protein, the introns must be removed through a process called RNA splicing. The remaining exons are then joined together to form a continuous coding sequence.


== Structure and Function ==
[[File:Exon-intron.svg|thumb|right|Diagram showing the structure of a gene with exons and introns.]]


Exons can be as short as two nucleotides or as long as several thousand. They are typically separated by introns, non-coding regions of DNA that do not contribute to the final protein product. During the process of RNA splicing, these introns are removed, and the exons are joined together to form a contiguous coding sequence.
The splicing of exons is a highly regulated process that allows for the generation of multiple protein isoforms from a single gene through [[alternative splicing]]. This increases the diversity of proteins that an organism can produce and plays a critical role in the regulation of gene expression.


Exons play a crucial role in the production of proteins, which are essential for the growth and repair of body tissues and the production of enzymes and hormones. They also play a role in the regulation of gene expression and the evolution of proteins.
==Role in Genetic Variation==
Exons are subject to various types of genetic variations, including [[mutations]], insertions, and deletions. These variations can have significant effects on the function of the resulting protein. For example, a mutation within an exon can lead to a change in the amino acid sequence of a protein, potentially altering its function or stability. Such mutations are often associated with genetic diseases and disorders.


== Exon Shuffling ==
==Exons in Evolution==
The exon-intron structure of genes is thought to have evolved to facilitate the modular assembly of proteins. Exons often correspond to functional domains of proteins, allowing for the recombination of exons to create new proteins with novel functions. This modularity is a key feature of [[evolutionary biology]], as it enables organisms to adapt to changing environments by evolving new protein functions.


[[Exon shuffling]] is a molecular mechanism that may contribute to the evolution of new proteins. It involves the recombination of exons within a gene or between genes, which can lead to new combinations of protein domains.
==Applications in Biotechnology==
 
Understanding the structure and function of exons is essential for various applications in [[biotechnology]] and [[genetic engineering]]. Techniques such as [[CRISPR-Cas9]] gene editing rely on precise knowledge of exon sequences to introduce targeted modifications in the genome. Additionally, exon analysis is crucial in the development of [[gene therapy]] strategies aimed at correcting genetic defects.
== Exon Skipping ==
 
[[Exon skipping]] is a form of RNA splicing used by cells to regulate gene expression. It involves the skipping of an exon during the splicing process, resulting in a protein with an altered amino acid sequence.
 
== Clinical Significance ==
 
Mutations in exons can lead to various genetic disorders. For example, [[Duchenne muscular dystrophy]] is caused by a mutation in the dystrophin gene that disrupts the reading frame, leading to an absence of the dystrophin protein. Similarly, [[Cystic fibrosis]] is often caused by a three-nucleotide deletion in the CFTR gene that results in the loss of a phenylalanine residue.
 
== See Also ==


==Related pages==
* [[Intron]]
* [[Intron]]
* [[Gene]]
* [[RNA splicing]]
* [[Alternative splicing]]
* [[Gene expression]]
* [[Protein synthesis]]
* [[Protein synthesis]]
* [[RNA splicing]]
* [[Exon shuffling]]
* [[Exon skipping]]
== References ==
{{reflist}}


[[Category:Genetics]]
[[Category:Genetics]]
[[Category:Molecular biology]]
[[Category:Biochemistry]]
{{stub}}
{{dictionary-stub1}}
<gallery>
File:Exon RNA_splicing_diagram_en.svg|Diagram showing RNA splicing
File:Gene_structure.svg|Illustration of gene structure
</gallery>

Latest revision as of 17:33, 18 February 2025

Detailed overview of exons in genetics


Overview[edit]

An exon is a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence. In the context of gene expression, exons are the portions of a gene that are transcribed into messenger RNA (mRNA) and are retained after the RNA splicing process. Exons are crucial for the synthesis of proteins, as they provide the necessary coding sequences that are translated into the amino acid sequences of proteins.

Structure and Function[edit]

Exons are interspersed with non-coding sequences known as introns. During the process of transcription, both exons and introns are initially copied into a precursor mRNA (pre-mRNA) molecule. However, before the mRNA can be translated into a protein, the introns must be removed through a process called RNA splicing. The remaining exons are then joined together to form a continuous coding sequence.

Diagram showing the structure of a gene with exons and introns.

The splicing of exons is a highly regulated process that allows for the generation of multiple protein isoforms from a single gene through alternative splicing. This increases the diversity of proteins that an organism can produce and plays a critical role in the regulation of gene expression.

Role in Genetic Variation[edit]

Exons are subject to various types of genetic variations, including mutations, insertions, and deletions. These variations can have significant effects on the function of the resulting protein. For example, a mutation within an exon can lead to a change in the amino acid sequence of a protein, potentially altering its function or stability. Such mutations are often associated with genetic diseases and disorders.

Exons in Evolution[edit]

The exon-intron structure of genes is thought to have evolved to facilitate the modular assembly of proteins. Exons often correspond to functional domains of proteins, allowing for the recombination of exons to create new proteins with novel functions. This modularity is a key feature of evolutionary biology, as it enables organisms to adapt to changing environments by evolving new protein functions.

Applications in Biotechnology[edit]

Understanding the structure and function of exons is essential for various applications in biotechnology and genetic engineering. Techniques such as CRISPR-Cas9 gene editing rely on precise knowledge of exon sequences to introduce targeted modifications in the genome. Additionally, exon analysis is crucial in the development of gene therapy strategies aimed at correcting genetic defects.

Related pages[edit]