L6. Control of Gene Expression Flashcards
how do cells differentiate
cells make and accumulate different sets of RNA and protein molecules
what are housekeeping genes
- genes that are common to all the cells of a multicellular organism
- cells contain ~50% of these genes
- they are used to characterize the differential expression of genes
what are examples of house keeping genes
- structural proteins of chromosomes
- ribosomal proteins
- enzymes involved in basic metabolic pathways
- cytoskeleton
- and more
how is gene expression regulated
- it is regulated at every step from DNA to protein:
1. transcriptional control
2. RNA processing control
3. mRNA transport and localization control
4. mRNA degradation control
5. translation control
6. protein degradation control
7. protein activity control
regulation of gene expression - transcriptional control
controlling when and how often a given gene is transcribed
regulation of gene expression - RNA processing control
controlling how an RNA transcript is sliced or otherwise processed
regulation of gene expression - mRNA transport and localization control
selecting which mRNAs are exported from the nucleus to the cytosol
regulation of gene expression - mRNA degradation control
regulating how quickly certain mRNAs molecules are degraded
regulating gene expression - translation control
selecting which mRNAs are translated into proteins by ribosomes
regulating gene expression - protein degradation control
regulating how rapidly specific proteins are destroyed after they have been made
transcriptional control - switches
- promoters
- regulatory DNA sequences
- transcription regulator proteins
transcriptional control: switches - promoters
they contain recognition sites for proteins that associate with the sigma factor (bacteria) or general transcription factors (eukaryotes)
transcriptional control: switches - regulatory DNA sequences
- used to switch the gene on or off
- can be upstream or downstream of the promoter
- they attract transcription regulator proteins
transcriptional control: switches - explain regulatory DNA sequences in prokaryotes vs eukaryotes
- prokaryotes: regulatory sequences are short and simple
- eukaryotes: sequences are longer and integrates multiple signals
transcriptional control: switches - transcription regulator proteins
these bind to the regulatory DNA sequence to act as the switch to control transcription
transcriptional control: switches - transcriptional regulator-DNA binding
- the transcription regulator positions itself within the major DNA groove as a dimer
- alpha-helices will tightly associate with DNA
bacterial mRNA - define polycistronic
prokaryotic mRNA can encode for several different proteins which are translated from the same mRNA molecule
bacterial mRNA - how are the different coding regions recognized
- they do not have a 5’ cap to tell the ribosome where to begin
- they instead have ribosome-binding sequences upstream the start codon
explain simple transcription switches in bacteria
- polycistronic transcripts and operon
- their gene regulation is dependent on the environment and available food sources
simple transcription switches in bacteria - define operon
- genes that are arranged in a cluster
- they are transcribed by a single promoter as one mRNA molecule
- the mRNA molecule then gives rise to multiple different proteins
simple transcription switches in bacteria - define operator
present within the operon’s promoter and it is recognized by a transcription regulator