Concept 17.2 Transcription is the DNA-directed synthesis of RNA: a closer look. Messenger RNA, the carrier of information from DNA to the cell’s protein-synthesizing machinery, is transcribed from the template strand of a gene. RNA polymerase separates the DNA strands at the appropriate point and joins the RNA nucleotides as they base-pair along the DNA template. o Like DNA polymerases, RNA polymerases can assemble a polynucleotide only in its 5 ′ 3 ′ direction. o Unlike DNA polymerases, RNA polymerases are able to start a chain from scratch; they don’t need a primer. Specific sequences of nucleotides along the DNA mark where gene transcription begins and ends. o RNA polymerase attaches and initiates transcription at the promoter. o In bacteria, the sequence that signals the end of transcription is called the terminator. Molecular biologists refer to the direction of transcription as “downstream” and the other direction as “upstream.” The terms downstream and upstream
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This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.