Final answer:
RNA dissociation during abortive initiation is often due to the formation of secondary structures such as hairpin loops within the RNA, which hinder RNA polymerase progression. Additionally, rho-independent termination sequences with weak U-A interactions contribute to the release of the RNA transcript, leading to the abortive initiation.
Step-by-step explanation:
RNA dissociation during abortive initiation is a phenomenon that is observed during the initial stages of transcription. In abortive initiation, RNA polymerase synthesizes short RNA oligonucleotides that are unable to proceed to elongation. A significant reason for this dissociation involves the formation of certain secondary structures, such as hairpin loops, within the newly synthesized RNA. These structures can cause physical hindrances to the progression of RNA polymerase, leading to stalling. Moreover, repetitive sequences rich in certain nucleotides, such as G nucleotides, can also cause polymerase stalling and eventual dissociation of the RNA.
Additionally, rho-independent termination signals can be present in the nascent RNA molecule. These consist of specific sequences that can form stable hairpin loops followed by a region of U-A nucleotides, which bind weakly to the DNA template. The combination of a stalled polymerase and the weak U-A interactions can create enough instability to cause RNA polymerase to release the RNA transcript prematurely, resulting in abortive initiation.