Question

g All base pairs in the genome are replicated during the DNA synthesis phase of the cell cycle, but only some of the base pairs are transcribed into RNA. How is it determined which base pairs of the genome are tran- scribed into RNA

Answer 1

Transcription is the process of forming RNA from DNA. Not all DNA sequences are transcribed. For transcription some factors are important like initiator sequence, transcription factors and termination sequence.

Only those genomic regions are transcribed which have an initiator sequence i.e. a promoter. RNA Polymerase needs to bind to the promoter region to begin transcription.

Similarly several factors are required which enhance the rate of transcription.

Terminator region is also important for transcription. When RNA Polymerase encounters it, it halts the transcription process.

Thus, only those base pairs of DNA are transcribed which have promoter and terminator regions. There should also be presence of many transcription factors otherwise transcription will not occur even when promoter and terminator regions are present.