LO13 Day 3 Flashcards
Cell regulation in prokaryotes occurs primarily because of what?
changes in their environment
In bacteria genes are organized into what to facilitate regulation?
operons
definition: a group of genes with related function and nearby DNA sequences that control the expression of genes
operon
What operon is involved in the catabolism of lactose?
lac operon
What functional genes are in the lac operon?
LacZ and LacY
what does lacZ do?
breaks down lactose
what does lacY do?
lets lactose enter the cell
definition: where RNA polymerase binds to DNA to transcribe the functional genes
promoter region
definition: determines whether or not the functional genes are transcribed?
operator region
where is an repressor gene located?
upstream of the operon
definition: codes for a protein that binds to the operator and block RNA polymerase
repressor gene
What does the repressor protein doe?
Keeps the operon turned off under certain environmental conditions
definition: controls expression of genes
operon
The lac operon is what kind of operon?
inducible
What happens when lactose is present in the environment?
it binds to the repressor proteina nd prevents it from binding to the operator
lactose is what to the repressor?
an allosteric inhibitor
What happens when the repressor protein is not bound to the operator?
RNA polymerase can transcribe to the functional genes…this is so cells can use lactose
What happens when lactose is not present in the environment?
the repressor protein stays bound to the operator
What happens when the repressor protein is m bound to the operator?
there is no transcription of the functional genes
definition: induces the expression of the genes needed
inducible operon
Where does lactose bind to the protein since it is an allosteric inhibitor?
To an allosteric site that is separate from an active site
Trp Operon is what kind of operon?
repressible operon
What happens when tryptophan is low in a bacteria cell?
the repressor protein cant bind to the operator and there is transcription of the functional genes that make the amino acid
what is tryptophan?
an amino acid
The repressor protein is made in what kind of form?
inactive
When tryptophan levels are high what happens?
the excess binds to the repressor protein and activates making it bind to the operator. There is no transcription of the functional genes
Tryptophan is an allosteric _______ of the repressor
activator
definition: represses the expression of the genes needed to be synthesized
repressible operon
inducible operons are part of ________ pathways whose genes need to be expressed only when substances are present in the environment.
catabolic
Repressible operons are part of ________ pathways whose genes need to be expressed only when substances are in low quantinty in the cell and need to be synthesized.
anabolic
gene regulation allows eukaryotes to do what for their cells?
develop and produce specialized
prokaryotes and eukaryotes primarily regulate gene expression at which level?
transcriptional level
definition: chromatin that is highly compacted
heterochromatin
definition: chromatin that is loosely compacted
euchromatin
Which chromatin is transcribed euchromatin or heterochromatin?
euchromatin
What is an example of heterochromatin?
The inactivated X chromosome in female mammals which is a Barr body.
Chemical modification of chromatin determines what?
chromosome structure
examples of chemical modification of chromosome are?
histone acetylation and DNA methylation
definition: addition of acetyl groups to histones
histone acetylation
histone acetylation is associated with the formation of which type of chromatin?
euchromatin and gene activation
DNA methylation is associated with the formation of which type of chromatin?
heterochromatin and gene inactivation
definition: addition of methyl groups to certain cytosine nucleotides
DNA methylation
Chemical modification are what?
epigenetic
definitions: inherited changes to DNA or chromosome structure that do not involve changing nucleotide sequence but do not affect gene expression
epigenetic modifications
definition: proteins that bind to DNA and interact with RNA polymerase at the promoter
transcription factors
example of transcription factors are?
many steroid hormones bind to intracellular receptors that function as transcription factors
definitions: DNA sequences that help form an active transcription comples and increase the rate of transcription
enhancers
definition: DNA sequences that decrease the rate of transcription
silencers
Are enhancers and silencers transcription factors or region of DNA?
silencer regions of DNA
definition: controlling gene expression by determining how or whether an mRNA transcript gets translated or not
posttranscriptional control
definition: molecules that bind to mRNAs and degrade them or prevent them from being translated are called what?
microRNAs (miRNA)
microRNAs are involves in a type of gene regulation called what?
RNA interference
definition: a single protein coding gene can produce different forms of its polypeptide in different tissues
alternative mRNA splicing
During alternative mRNA splicing the gene will have at lease one segment that can be either ______________ depending on the tissue
intron or exon
The gene created during alternative mRNA splicing produces the same _____ but slightly different ________
pre mRNA; mature mRNA
How do microRNAs work?
They block translation or degrade mRNA
This control affects translation
posttranscriptional
This control regulates proteins
posttranslational
chemical modification to already translated protein can do what to them?
activate or deactivate them
What do kinases do?
they are enzymes that add P groups to other proteins which activates them
What do phosphatases do?
They remove P groups usually deactivating proteins
definition: eliminates unneeded proteins from cell.
protein degradation
Which proteins are degraded by proteasoemes
the ones bonded to ubiquitin molecules
definition: protein-digesting organelles that contain protein degrading enzymes
proteasomes
