The word "exons" (IPA: /ˈek.sɒnz/) refers to the segments of DNA that code for proteins. The spelling of the word is based on the Latin prefix "ex-" meaning "out of" and the word "intron" which refers to the non-coding segments of DNA. The phonetic transcription shows that the stress is on the first syllable, and the "o" sound is pronounced as "ɒ". The "s" at the end of the word tells us that it is plural, indicating the presence of multiple exons in a given gene.
Exons are segments of DNA or RNA molecules that are transcribed into mature messenger RNA (mRNA) molecules. In genetics, exons are the coding regions of genes that contain the instructions for building proteins. They are distinct from the noncoding regions called introns, which are later removed during mRNA processing through a process known as splicing.
Exons play a crucial role in the protein synthesis process. They contain the genetic code that specifies the sequence of amino acids that make up a protein. Each exon codes for a specific portion of the protein, and the arrangement and order of exons ultimately determine the final structure and function of the protein.
During the process of gene expression, the DNA sequence containing both exons and introns is transcribed into pre-mRNA. Pre-mRNA undergoes splicing, where the introns are removed, leaving only the exons. This processing step results in the formation of mature mRNA molecules, which are then transported out of the nucleus and serve as templates for protein synthesis.
Exons can vary in size and number among different genes, and their arrangements can differ as well. Mutations in exons can cause various genetic disorders, as they can disrupt the proper functioning of proteins or even result in the absence of functional proteins.
In summary, exons are the coding regions of genes that contain the necessary information for building proteins. They undergo splicing to remove introns and give rise to mature mRNA molecules, which are responsible for protein synthesis.
The word "exons" is derived from the term "exon", which itself is a contraction of "expressed sequence of DNA". The term "exon" was first coined in 1978 by Walter Gilbert, a molecular biologist and Nobel laureate, to describe the coding regions of genes. These are the regions of DNA that contain the instructions for producing proteins. The prefix "ex-" means "out of" or "from", implying the idea that exons are the expressed or functional portions of DNA. Over time, the plural form "exons" came into use to collectively refer to multiple coding regions within a gene or a genome.