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  • In a nucleus, the number of ribonucleoside triphosphates is 10 times the number of deoxy x10 ribonucleoside triphosphates, but only deoxyribonucleotides are added during the DNA replication. Suggest a mechanism.

In a nucleus, the number of ribonucleoside triphosphates is 10 times the number of deoxy x10 ribonucleoside triphosphates, but only deoxyribonucleotides are added during the DNA replication. Suggest a mechanism.

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The mechanism behind this selective incorporation of deoxyribonucleotides during DNA replication, despite the higher concentration of ribonucleoside triphosphates (rNTPs) in the nucleus, lies in the specificity of the DNA polymerase enzyme. DNA polymerases are highly selective for deoxyribonucleotides (dNTPs) during replication due to their active site structure, which accommodates only the 2'-deoxyribose sugar present in dNTPs, excluding the 2'-hydroxyl group found in ribonucleotides (rNTPs). Additionally, the ATP-dependent action of ribonucleotide reductase ensures the appropriate balance of dNTPs by converting rNTPs to their deoxy counterparts, thus providing the necessary pool of deoxyribonucleotides for DNA synthesis while preventing the incorporation of ribonucleotides into the growing DNA strand. Therefore, it cannot hold RNA nucleotides.

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