Genetics Ex 2 Book ?'s

What is meant by constitutive gene expression? How is constitutive gene expression unlike regulated gene expression? What can you infer about the site of a mutation that causes constitutive expression of a protein that normally shows regulated expression?

-Genes that are always active in cells are constitutive (or house-keeping genes). -Constitutive gene expression refers to gene expression that is constantly present, while regulated gene expression refers to gene expression that is controlled in response to the needs of a cell or organism. -That there is a mutation at the site that normally regulates expression. In bacterial operon: mutation in the operator could prevent the binding of a transcriptional repressor. Or a mutation in the gene for the repressor could prevent the repressor from binding to the operon. Both causing constitutive expression.

Give 2 examples of effector molecules, and discuss how effector molecules function to regulate gene expression.

tryptophan and allolactose are effector molecules that affect the lap and trp operons. -Effectors allow allosteric shifts in repressor proteins to alter their affinity for operator sites in DNA. -allolactose: binds to the lac repressor, it loses it affinity for the lac operator, INDUCING transcription -tryptophan: when it interacts with the aporepressor, it is converted into an active repressor that can bind to the trp operator, REPRESSING TRANSCRIPTION at the trp operon