# Coding strand

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{{short description|DNA strand with the same base sequence as an mRNA transcript}}
[[File:Process of DNA transcription.png|alt=Two linear DNA strands are separated by a blue oval, which is creating RNA by running along the template strand. The coding strand is above, not attached to RNA polymerase.|thumb|400x400px|Position of the template and coding strands during [transcription](/source/Transcription_(biology)).]]
When referring to [DNA transcription](/source/Transcription_(genetics)), the '''coding strand''' (or '''informational strand'''<ref>{{Cite web|date=2015-08-26|title=28.4: Transcription of DNA|url=https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(McMurry)/28%3A_Biomolecules_-_Nucleic_Acids/28.04%3A_Transcription_of_DNA|access-date=2021-09-06|website=Chemistry LibreTexts|language=en}}</ref><ref>{{Cite book|last=STOKER|first=H. STEPHEN|title=General, Organic, and Biological Chemistry|publisher=Cengage Learning|year=2013|pages=816}}</ref>) is the [DNA](/source/DNA) strand whose [base](/source/Nucleobase) sequence is identical to the base sequence of the [RNA](/source/RNA) transcript produced (although with [thymine](/source/thymine) replaced by [uracil](/source/uracil)). It is this strand which contains [codons](/source/codons), while the non-coding strand contains [anticodon](/source/anticodon)s. During transcription, [RNA Pol II](/source/RNA_polymerase_II) binds to the non-coding '''template strand''', reads the anti-codons, and transcribes their sequence to synthesize an RNA transcript with complementary bases.

By convention, the coding strand is the strand used when displaying a DNA sequence. It is presented in the [5' to 3' direction](/source/Directionality_(molecular_biology)).

Wherever a [gene](/source/gene) exists on a DNA [molecule](/source/molecule), one strand is the coding strand (or '''sense strand'''), and the other is the '''noncoding strand''' (also called the [antisense](/source/sense_(molecular_biology)) strand,<ref name="Lewin08">{{cite book|url=https://books.google.com/books?id=BrNpbPkzoxAC&pg=PA129|title=Genes IX|last=Lewin|first=Benjamin|publisher=Oxford University Press|year=2008|isbn=978-0-7637-4063-4|page=129, 235}}</ref> anticoding strand, '''template strand''' or''' transcribed strand''').

==Strands in transcription bubble==
During [transcription](/source/Transcription_(genetics)), [RNA polymerase](/source/RNA_polymerase) unwinds a short section of the DNA [double helix](/source/double_helix) near the start of the gene (the transcription start site). This unwound section is known as the [transcription bubble](/source/transcription_bubble). The RNA polymerase, and with it the transcription bubble, travels along the noncoding strand in the opposite, 3' to 5', direction, as well as polymerizing a newly synthesized strand in 5' to 3' or [downstream](/source/Upstream_and_downstream_(DNA)) direction. The DNA double helix is rewound by RNA polymerase at the rear of the transcription bubble.<ref name=Lewin08/> Like how two adjacent zippers work, when pulled together, they unzip and rezip as they proceed in a particular direction. Various factors can cause double-stranded DNA to break; thus, reorder genes or cause cell death.<ref name="pmid28868264">{{cite journal |vauthors = Dianatpour A, Ghafouri-Fard S |title = The Role of Long Non Coding RNAs in the Repair of DNA Double Strand Breaks|journal =   International Journal of Molecular and Cellular Medicine|volume = 6 |issue = 1 |pages = 1–12 |year = 2017 |pmid = 28868264 |pmc = 5568187}}</ref>

==RNA-DNA hybrid==
Where the helix is unwound, the coding strand consists of unpaired bases, while the template strand consists of an RNA:DNA composite, followed by a number of unpaired bases at the rear. This hybrid consists of the most recently added [nucleotides](/source/nucleotides) of the RNA transcript, complementary base-paired to the template strand. The number of base-pairs in the hybrid is under investigation, but it has been suggested that the hybrid is formed from the last 10 nucleotides added.<ref>{{harvnb|Griffiths|2005|pp=259–265}}</ref> 

== See also ==
* [Sense strand](/source/Sense_strand)
* [Sense (molecular biology)](/source/Sense_(molecular_biology))

==References==
{{reflist}}

==Works cited==
*{{cite book |last1=Griffiths |first1=A.J.F.  |title=Introduction to Genetic Analysis |publisher=W.H. Freeman |year=2005 |isbn=0-7167-4939-4 |edition=8th |display-authors=etal}}
*{{cite book |author=Lewin, B. |title=Genes VII |url=https://archive.org/details/genesvii00lewi |url-access=registration |publisher=Oxford University Press |location=New York |year=2000 |isbn=0-19-879277-8 }}

Category:Molecular biology
Category:DNA

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Adapted from the Wikipedia article [Coding strand](https://en.wikipedia.org/wiki/Coding_strand) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Coding_strand?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.