Control mechanisms Flashcards
What are housekeeping genes
genes that are always needed and are constantly transcribed
what does being transcribed mean
In transcription, the DNA sequence of a gene is transcribed (copied out) to make an RNA molecule.
Types of control?
Transcriptional
Posttranscriptional
translational
posttranslational
Define transcriptional control
transcriptional control regulates which genes are transcribed (DNA to mRNA) or controls the rate of transcription
Define Posttranscriptional control
Posttranscriptional controls mRNA undergoing changes in the nucleus before translation, introns are removed and exons are spliced together
Define translational control
controls how often and how rapidly mRNA
transcripts will be translated into proteins
affects the length of time it takes to activate
mRNA and the speed of the enzymes which
destroy the mRNA
Define posttranslational control
posttranslational
before proteins become functional they must pass through the cell membrane, a number of
control mechanisms affect the rate at which a protein becomes active
define operons
a cluster of genes under the control of one promoter and one operator
Where is operons found in
found in prokaryotic cells only
LAC OPERON
What does it regulate?
what does it consist of
what does the LAC1 repressor do
what does high levels of lactose induce and where is this thingy made from
when is lactose a inducer
The lac Operon
regulates the production of β-galactosidase and other proteins involved in the metabolism of lactose
consists of a cluster of three genes controlled by one promoter and one operator
the lac1 repressor protein binds to the operator when lactose levels are low, therefore blocking RNA polymerase from transcribing the gene
high levels of lactose induce the operon because lactose binds to the lac1 repressor protein, changing its shape, and thus preventing it from being able to bind to the lac operon.
in this case, lactose is referred to as an inducer (It binds to a
repressor protein to cause transcription)
The trp Operon
regulates the production of the amino acid tryptophan
consists of a cluster of five genes controlled by one promoter and one operator
when tryptophan levels are low, the trp repressor is not attached to the operator (its shape will not allow it to bind), so transcription of the gene occurs
when tryptophan levels are high, the tryptophan binds to the trp repressor
protein, changing its shape, and the complex then binds to the operator,
therefore blocking transcription (repressing the operon)
in this case, tryptophan is referred to as a corepressor (It binds
to a repressor molecule to activate the repressor molecule and
block transcription)
Trp Operon
what does it regulate
what does it consist of
what happens when tryptophan levels are low?
what happens when tryptophan levels are high
why is it called a corepressor
regulates the production of the amino acid tryptophan
consists of a cluster of five genes controlled by one promoter and one operator
when tryptophan levels are low, the trp repressor is not attached to the
operator (its shape will not allow it to bind), so transcription of the gene occurs
when tryptophan levels are high, the tryptophan binds to the trp repressor protein, changing its shape, and the complex then binds to the operator, therefore blocking transcription (repressing the operon)
in this case, tryptophan is referred to as a corepressor (It binds
to a repressor molecule to activate the repressor molecule and
block transcription)
order of the Lactose genes in Lac operon diagram
LAC Z, LAC Y, LAC A
gene regulation or gene regulation mechanisms
controlling transcriptin/translation
ex
Lac and trp operons
what is a signal molecule
molecule that binds to the repressor to change its shape
