Biochemistry 2280A Lecture Notes - Lecture 23: Trp Operon, Sigma Factor, Transcription Bubble
10 Dec 2016
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Gene dosage in our genome we have two copies of each gene. We can"t get differential gene expression because each gene has two. The rna step provides amplification which contributes to differential gene expression: different numbers of rnas made from each gene. Since rna can be degraded (it is fairly unstable), expression of a gene can be stopped quickly. Rna provides additional opportunities to regulate gene expression (ex. Highly regulated step in gene expression for many genes. Promoter: the dna sequence required to initiate transcription of a gene or operon. Terminator: the dna sequence required to stop transcription. Operon: a set of genes transcribed from a single promoter and thus expressed from a common rna, unique terminal for prokaryotes (specific) Start site of transcription is called +1. All protein encoding genes associated with a single rna synthase. 10 sequence (tataat), 10 bases before (upstream) promoter (+1) 35 sequence (ttgaca), 35 bases before promoter: specific, 6 bases in length.
