BI236 Lecture Notes - Lecture 8: Transcription (Genetics), Sigma Factor, Start Codon
Document Summary
The genetic code: one start codon (aug, met, three stop codons (uaa, uag and uga, mutations in the third base of a codon, frequently do not change the specified amino acid at all, genetic code is nearly universal. Transcription of mrna from dna: template strand and non-template strand (coding strand, utilizes the same base pairing rules as dna replication, except uracil (u) in place of thymine, since mrna molecules are synthesized in the. 5" 3" direction (like dna), 64 codons are also written in 5" 3" direction. Involves four stages; binding, initiation, elongation and termination. Transcription of bacteria: rna polymerase binds to promoter, sigma ( ) factor. Initiation of synthesis: elongation of rna, termination of synthesis, termination signal - use of gc loop or rho factor". Organization of bacterial promoter sequence: start point - designated +1", six-nucleotide sequence at -10 (tataat) called - 10 sequence" or pribnow box": six nucleotide sequence at -35 (ttgaca) called -