When does the nucleus of a cell "know" when to bind DNA nucleotides ( for Replication ) or RNA nucleotides ( for Transcription ). From what i read, they're both structurally different and free nucleotides of both are present in the nucleoplasm. So when one's free nucleotides bind ( mRNA nucleotides for transcription for example ) why doesn't the other ( DNA nucleotides in this case )bind, or what keeps the other from doing so?

Are their any chemical prerequisites of some sort that initiate the processes?


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    $\begingroup$ Your question is too broad for this list, where question sof this sort assume some basic familiarity with the topics asked. You need to read about replication and transcription in some introductory book of biochemistry. Berg et al. on NCBI Bookshelf has well written chapters on these topics. $\endgroup$ – David Oct 8 '18 at 21:21

Enzymes, nature’s catalysts, proteins that speed up chemical reactions. In this case, creating a linear polymer out of deoxribonucleotide monomers, to yield a polynucleotide (DNA). This reaction also requires a DNA template strand. Enzymes contain an active site that brings all of the substrates into alignment, and then key amino acid side chain residues that are located in the active site enhance the intended organic chemical reaction, often by stabilizing a transition state in one or more of the substrates.

You are correct that ribonucleotides and deoxyribonucleotides share many structural similarities, but enzyme active sites can indeed distinguish between the two molecules. Even if the wrong substrate diffuses into the active site it will usually not be able to participate in the reaction.

  • $\begingroup$ Oh ok so basically, its the Polymerase enzymes that sort of "filter" out the right nucleotide additions form the wrong ones and the nucleotides connect to the strand all in their due time? $\endgroup$ – Kazi Oct 11 '18 at 3:01

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