BIO130H1 Lecture Notes - Lecture 9: Sigma Factor, Enzyme, Phosphodiester Bond

• School: UTSG
• Department: Biology
• Course: BIO130H1
• Professor: Melody Neumann, Kenneth Yip

Document Summary

Generation of an rna transcript: template: single-stranded dna (ssdna, rna linked by phosphodiester bonds, polymerase facilitates the reaction to produce the phosphodiester bonds, dna-rna hybrid held together by base pairing. The transcription cycle: holoenzyme = sigma factor + rna polymerase, sigma factor binds to core enzyme and binds to promoter. In bacteria, there are different sigma factors that recognize different genes: this is the way by which bacteria regulate which genes are being expressed. Initial rna synthesis: several short rnas cast off, sigma factor releases, rnap enters processive mode and sigma factor is released, rna elongation, termination, lots of g-cs followed by lots of a-ts. Model of gene expression: polycistronic mrna generating multiple proteins from one transcript, allows bacteria to use a single promoter with the same type of sigma to coordinate expression of all the genes. Note: introns are sequences that are removed before the final mrna is made.