Which of the following modifications occurs to the RNA polymerase tail in order to trigger it to elongate the transcript?

Genomic DNA from a mouse is isolated, fragmented, and denatured into single strands. It is then mixed with mRNA isolated from the cytoplasm of mouse cells. The image represents an electron micrograph result showing the hybridization of single-stranded DNA and mRNA.

Which nucleic acid is indicated by the 'b' pointer? Justify your answer. 

Genomic DNA from a mouse is isolated, fragmented, and denatured into single strands. It is then mixed with mRNA isolated from the cytoplasm of mouse cells. The image represents an electron micrograph result showing the hybridization of single-stranded DNA and mRNA.

Which nucleic acid is indicated by the 'a' pointer? Justify your answer. 

Which of the following polymerases is responsible for transcribing mRNA in eukaryotes?

Which of the following general transcription factors is responsible for binding to the TATA-Box

Which of the following regulatory mechanisms regulates transcription from a great distance away from the gene?