BIOLOGY 1A03 Lecture Notes - Lecture 11: Prokaryote, Sickle-Cell Disease, Polyploid

• School: McMaster University
• Department: Biology
• Course: BIOLOGY 1A03
• Professor: Daniel Yang

Document Summary

Sigma is regulatory component and core enzyme contains the active site. Fig 16. 3 - in bacteria, sigma plays a key role in. Sigma must rst bind to rna polymerase to form a holoenzyme. Holoenzyme also consists of core enzyme which contains active site for catalysis. Holoenzyme binds tightly to promotors - where transcription of bacterial genes is initiated. Sigma appears to be responsible for guiding rna polymerase to promotors. Promotors - located on non-template strand, 40-50 bps long, have particular section that look similar. Promotors have two key regions: -10 box (10 bp upstream transcription start site) and -35 box (35 bp upstream) Transcription begins when sigma binds to -35 and -10 boxes, and then dna helix opens. Template strand is threaded through rna polymerase active site. Ntp"s (ribonucleoside triphosphate) pair with a complementary base on dna template strand, and rna polymerization begins. Sigma dissociates from core enzyme once the initiation phase of transcription is completed.