Question

If cordycepin triphosphate is added to a cell-free transcription reaction, the nucleotide is added onto the growing rna chain but no more nucleotides can then be added. the added cordycepin is always found at the 3' end of an rna. examine the structure of cordycepin and explain why it ends transcription.

Answer 1

During elongation of RNA or synthesis of DNA, nucleotides are joined in chains by chemically joining the 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of the next nucleotide. Cordycepin triphosphate is similar in structure to the adenosine triphosphate hence is incorporated in elongation chain during transcription and replication. However, due to its lack of the 3’OH moiety (that is required for elongation), the replication or transcription is unduly terminated.