An Echo, a Stain
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Is DNA helicase or DNA polymerase responsible for breaking hydrogen-bonds during transcription? There are two textbooks which claim it is the former, as well as a YouTube video on the topic by Miss Estruch. On the other hand, Seneca for AQA claims 'where RNA polymerase binds to DNA, the hydrogen bonds that bind the two strands together break. This is different to DNA replication, where DNA helicase breaks the strands,' online results are varied for example this (https://en.wikiversity.org/wiki/Effe...en_bond_on_RNA) claims 'RNA polymerase unwinds/"unzips" the DNA by breaking the hydrogen bonds.' The third book in question in one from Oxford approved by AQA: it remains vague attributing this bond-breaking to 'an enzyme.' Got exams in 4 days, feelsbadman
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qwert7890
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(Original post by An Echo, a Stain)
Is DNA helicase or DNA polymerase responsible for breaking hydrogen-bonds during transcription? There are two textbooks which claim it is the former, as well as a YouTube video on the topic by Miss Estruch. On the other hand, Seneca for AQA claims 'where RNA polymerase binds to DNA, the hydrogen bonds that bind the two strands together break. This is different to DNA replication, where DNA helicase breaks the strands,' online results are varied for example this (https://en.wikiversity.org/wiki/Effe...en_bond_on_RNA) claims 'RNA polymerase unwinds/"unzips" the DNA by breaking the hydrogen bonds.' The third book in question in one from Oxford approved by AQA: it remains vague attributing this bond-breaking to 'an enzyme.' Got exams in 4 days, feelsbadman
From what I know, DNA Helicase breaks hydrogen bonds whereas RNA Polymerase (not DNA polymerase) catalyses the formation of phosphodiester bonds between nucleotides to assemble the mRNA during transcription.

From what I have seen online, however, it also seems that RNA Polymerase is in fact capable of also breaking hydrogen bonds aside from its normal role. However, for the purposes of exams, you should refer to DNA Helicase only when talking about hydrogen bonds being broken.

Here is an example past question from AQA itself (look at 11.1) and then look at the mark scheme. It appears your exAm board recognises only DNA Helicase and hence you should mention only this.

https://filestore.aqa.org.uk/resourc...ESOURCES-A.PDF
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An Echo, a Stain
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(Original post by qwert7890)
From what I know, DNA Helicase breaks hydrogen bonds whereas RNA Polymerase (not DNA polymerase) catalyses the formation of phosphodiester bonds between nucleotides to assemble the mRNA during transcription.

From what I have seen online, however, it also seems that RNA Polymerase is in fact capable of also breaking hydrogen bonds aside from its normal role. However, for the purposes of exams, you should refer to DNA Helicase only when talking about hydrogen bonds being broken.

Here is an example past question from AQA itself (look at 11.1) and then look at the mark scheme. It appears your exAm board recognises only DNA Helicase and hence you should mention only this.

https://filestore.aqa.org.uk/resourc...ESOURCES-A.PDF
Merki, thanks. Found this: 'In prokaryotes, RNA polymerase catalyses every step of transcription including the separation of the DNA strands and the production of the mRNA strand. In eukaryotes, RNA polymerase only produces the mRNA strand, whilst another enzyme called DNA helicase separates the DNA strands.' As the question in the link mentions the nucleus I suppose it is eukaryotic (maybe AQA avoids prokaryotic transcription).
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