Final answer:
The energy for an intrinsic terminator to function comes from the kinetic energy of the moving RNA polymerase. This is made possible through the energy released from the incorporation of ribonucleotide 5' triphosphates into the growing RNA strand, not external energy sources like ATP or NADP.The correct option is A.
Step-by-step explanation:
The source of energy that allows an intrinsic terminator to function is the kinetic energy of the moving RNA polymerase. During transcription, RNA polymerase unwinds the DNA template and adds nucleotides to the growing RNA strand.
This process does not require external energy sources such as ATP, thermal energy, or NADP because the energy needed is provided by the ribonucleotide 5' triphosphates (NTPs) such as ATP, UTP, CTP, and GTP which are present in the transcription environment.
When a ribonucleotide is added to the growing RNA strand, the high-energy bonds with the phosphates are broken, and the energy released during this reaction is what drives the polymerization forward.
Intrinsic terminators function as a result of the RNA polymerase encountering a specific DNA sequence which causes the synthesized RNA to form a hairpin loop, followed by a region of uracil (U) bases.
This hairpin structure causes the polymerase to stall, and because uracil forms only weak interactions with adenine in the DNA, the RNA-DNA hybrid in this region is unstable, leading to the dissociation of the RNA transcript and termination of transcription.The correct option is A.