Lecture 12: Gene Expression Flashcards
How do we regulate gene expression in bacterial cells (prokaryotic)
lac operons
What are the two kinds of operons in prokaryotic cells
-inducible: the transcription is usually off but can be stimulated
-repressible: the transcription is usually on but can be inhibited (repressed)
What type of operon is the lac operon
repressed off
When is the lac operon on? When it is off?
On: lactose only present
Off: glucose only present
off: both glucose and lactose are present
What happens when glucose is present?
it inhibits adenylyl cyclase, no cAMP, cannot form CAP/cAMP complex, cannot initiate transcription
What happens when lactose is present?
a small amount of allolactose is produced that binds to the repressor and prevents it from binding to the operator
In terms of eukaryotic cells:
What are the two types of regulatory molecules?
-Cis acting elements, part of the DNA
-Trans acting elements: proteins and transcription factors
What are the streps of transcriptional regulation by steroid hormones
- binding of a steroid hormone to its nuclear receptor which causes a conformational change in the receptor that uncovers its zinc finger. DNA binding domain
- the hormone receptor complex interacts with specific regulatory DNA sequence such as GRE
- The hormone receptor complex in association with coactivator proteins control the trans scripting of target genes
What is alternative splicing
a cellular process in which exons from the same gene are joined in different combinations, leading to different, but related, mRNA transcripts
ex: 1, 2, 3, 4, 5 or 1, 2, 4, 5
What is an example of alternative splicing in the body
tropomyosin having different forms in different tissues
____________ a widespread and conserved regulatory mechanism that generates diverse 3′ ends on mRNA
Alternative polyadenylation (APA)
What is an example of Alternative polyadenylation in body
production of two different IG molecules: membrane bound IgM and IgD
__________: modification in which 1 base in the mRNA is altered
Give an example
mRNA editing
Example: liver and small intestine cell produce apBs of different lengths
What is an example of mRNA stability
regulation of transferring receptor protein TfR expression by iron
RNA interference is the Mechanism of reducing gene expression by either: (2 things)
‣ repressing translation
‣ increasing the degradation of specific mRNAs
RNA interference is Mediated by:
(2 things)
‣ Endogenously produced short micro RNAs (miRNA)
‣ Exogenous short interfering RNAs (siRNA)
______________:
‣ Fundamental role in cell proliferation,
differentiation, and apoptosis (miRNA)
‣ Widely used as tool in research
‣ Huge therapeutic potential: currently more than 50
are in clinical trials for various diseases
RNA interference:
________________________________
Mobile segments of DNA (transposones, Tn)
that move in a random manner from one
site to another on the same or a different
chromosome
✓Enzyme mediated (transposase)
✓Movement can be:
✓Direct - transposase cuts out and then
inserts the Tn at a new site
✓Replicative - Tn is copied and the copy
inserted elsewhere while the original
remains in place.
✓Role - in genome structural variations
Transposition
What are some examples of transposition
Duchene muscular dystrophy
Rare cases of hemophilia A
Antibiotic resistance in bacteria
__________________: Play a role in the generation of 109−1011
different immunoglobulins from a single
gene, providing the diversity needed for
the recognition of an enormous number of
antigens
rearrangement of DNA
What are some clinical examples of regulation of DNA
pathologic DNA rearrragment is seen with chromosomal translocations in which two different chromosomes exchange DNA segments
