BIO230H1 Chapter Notes - Chapter 3: Purine, Guanine, Circadian Clock
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BIO230H1 Full Course Notes
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Document Summary
Cell memory: cells can remember the pattern of fne expression and pass on to daughter cells through subsequent cell divisions. Positive feedback loop is the most prevalent way. Transcription circuits allow the cell to carry out logic operations. If a is only a brief signal not long enough to activate b no output. If a persits b can be activated output is transcribed. Operates after rna polymerase has bound to the gene"s promoter. Transcription attenuation causes the premature termination of some rna molecules. Transcription attenuation : when the expression of some genes inhibited by premature termination of transcription. Riboswitches probably represent ancient forms of gene control. Riboswitches: short sequences of rna that change their conformation on binding small molecules. Example : a riboswitch that responds to guanine. When guanine low: rna polymerase transcribes purine biosynthetic genes. When guanine abundant: genuine bind to riboswitch forces rnap to terminate. Circadian clocks contain negative feedback loops that control gene expression.
