Final answer:
Replacing the 3'-end blocking groups in reversible terminator sequencing with 3'-hydrogen as in dideoxynucleotides would impede the reversible aspect of the sequencing, turning it into a form of chain termination method akin to Sanger sequencing, and eliminating the high-throughput advantages of the newer technologies.
Step-by-step explanation:
The question pertains to reversible terminator sequencing, a DNA sequencing method in which modified nucleotides are used to temporarily halt the synthesis of DNA strands, allowing for the sequencing process to occur one base at a time. If, hypothetically, the 3'-end blocking groups of each nucleotide in reversible terminator sequencing were replaced with a 3'-hydrogen (3'-H), which is present in the dideoxynucleotides used in Sanger sequencing, sequencing would be significantly impacted. The presence of a 3'-H in dideoxynucleotides means that once incorporated, they prevent further elongation of the DNA strand, effectively terminating synthesis. This is because the critical 3' hydroxyl group (3'-OH) necessary for forming a phosphodiester bond with the next incoming nucleotide is absent.
In the context of reversible terminator sequencing, using a reversible blocking group instead allows for the temporary halting of synthesis, which, once the block is removed (which is why it's termed 'reversible'), enables the extension to continue. If dideoxynucleotides were used in this sequencing method, chain extension could not resume after the incorporation of these nucleotides, thus undermining the entire principle of the reversible aspect of the method. This would essentially convert the process into the dideoxy chain termination method, or Sanger sequencing.