Firstly, flanking the open reading frame, all genes contain a regulatory sequence that is required for their expression. In order to be expressed, genes require a promoter sequence. The promoter is recognized and bound by transcription factors and RNA polymerase to initiate transcription.:7.1 A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end. Promoter regions have a consensus sequence, however highly transcribed genes have "strong" promoter sequences that bind the transcription machinery well, whereas others have "weak" promoters that bind poorly and initiate transcription less frequently.:7.2 Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.:7.3 COUNT 5
QSN1 What do all genes contain that is required for their expression? ANS1 a regulatory sequence QSN2 How is a promoter sequence recognized? ANS2 by transcription factors and RNA polymerase QSN3 What results when genes have more than one promoter? ANS3 messenger RNAs (mRNA) that differ in how far they extend in the 5' end QSN4 What does a "strong" promoter sequence do? ANS4 bind the transcription machinery well QSN5 What does a "weak" promoter sequence do? ANS5 bind poorly and initiate transcription less frequently