Control of transcription initiation

CONSTITUTIVE EXPRESSION - Some genes are always expressed. 2 general transcriptional mechanisms: INDUCTION - the switching on of genes when they are required REPRESSION - the switching off of genes when they are not required. Repressors are regulatory proteins which prevent transcription when bound to the DNA, activated by co-repressors. Activators are regulatory proteins which activate transcription when bound to the DNA, activated by inducers.