genes, operon, trp #2 Flashcards
gene regulation
the process of switching a gene on and off
developmental
genes are switched on/off as we reach puberty and then again during menopause
environmental
genes can be switched on and off as the environment changes
-sun exposure
physiological
genes can be switched on and off due to metabolic process in our cells
types of genes
- regulatory genes
- structural genes
regulatory genes
involved in controlling the expression of other genes
- the product regulates the expression of another gene.
structural genes
genes that are not regulatory
- regulated by regulatory genes
operons
a group of genes that all share the same promotor region - TATA box
- a collection of genes under the control of one regulatory gene
- regulatory gene is not part of the operon-
parts of the trp operon
- promotor region
- operator region
- structural genes
promotor region
where the RNA polymerase attaches
operator region
where the repressor protein attaches
- tells you whether or not transcription happens
structural genes pt 2- in operon
the genes that code for the enzymes which are required to synthesize tryptophan
trp- the regulatory gene
- located before operon
- codes for a protein that controls the transcription of the gene in the operon
low levels of tryptophan
the genes that code for the necessary enzymes must be expressed
- the transcription factor(repressor protein) is inactive so it cant bind to the operator site- because it is not the right shape- needs 2 tryptophan to attach in order for it to bind to the operatr site , meaning RNA polymerase can pass over the 5 structural genes and transcribe them
- the enzymes used to make tryptophan are then produced
when tryptophan is present:
there is no need for the cell to make more so the operon is turned off.
the operon can be turned off by:
- repression
- attenuation
repression
prevents the initiation (beginning) of transcription
attenuation
prevents the completion of transcription
