Lecture 16- Gene Regulation Flashcards
What are constitutive genes?
Genes that are always needed and constantly transcribed
What is an operon?
Cluster of functionally-related genes that are controlled by a shared operator
True or False: Operons are found in both eukaryotic and prokaryotic cells
False; operons are only found in prokaryotes
How does histone methylation differ from histone acetylation?
Histone methylation reduces transcription whereas histone acetylation promotes transcription
What are the three genes for lactose metabolism in E. coli?
Lac Z / Lac Y / Lac A
True or false: In the absence of lactose, the Lac Operon will continue to transcribe Lac genes
False; the Lac Operon will not transcribe in the absence of lactose
What is the function of the repressor in the Lac Operon?
Prevents transcription
Inducer
On/off switch (where RNA polymerase has to pass through)
How does the repressor become activated?
Inducer activates repressor
What is an inducible gene?
Gene that is usually off (transcription needs to be turned on → inducer inactivates repressor)
What is the inducer in the Lac Operon?
Allolactose (isomer of lactose)
How does the inducer function in the Lac Operon?
Allolactose (inducer) binds to repressor and changes its shape → allows RNA polymerase to bind to promoter and transcribe gene
True or false: Prokaryotes can regulate gene expression through various different mechanisms
False; prokaryotes can only regulate gene expression at transcription via operons
True or false: The Lac Operon is considered a repressible operon
False; the Lac Operon is an inducible operon
True or false: In the presence of lactose and absence of glucose, the repressor is tightly bound to the operator
False; in the presence of lactose and absence of glucose, the inducer (allolactose) will bind to the repressor, causing it to dissociate from the operator
How are glucose and cAMP related?
Glucose and cAMP are inversely proportional. The presence of glucose inhibits the production of cAMP & the absence of glucose facilitates cAMP production (low glucose → high cAMP / high glucose → low cAMP)
What is the function of cAMP in the Lac Operon?
cAMP activates CAP
What is the function of CAP in the Lac Operon?
CAP binds to promoter and facilitates RNA polymerase in binding to DNA template
How can eukaryotic cells regulate gene expression at the level of chromatin?
Formation of heterochromatin (tightly coiled chromatin) → inactive/inaccessible genes even during interphase (barr body for example)
How can eukaryotic cells regulate gene expression at the level of transcription?
Aid or inhibit the attachment of RNA polymerase and/or transcription factors
How can eukaryotic cells regulate gene expression at the level of the nucleosome?
Histone methylation to reduce transcription or histone acetylation to promote transcription
How can eukaryotic cells regulate gene expression post-transcription?
Alternative splicing (introns/exons/5 G cap/3 poly-A tail)
What is the difference between euchromatin and heterochromatin?
Heterochromatin is tightly coiled and therefore does not allow for transcription whereas euchromatin is loosely packed and allows for transcription
By which process can a single individual gene be rendered inactive?
DNA methylation (methyl group added to cytosine → makes DNA hydrophobic → inhibits gene expression)
How can eukaryotic cells regulate gene reexpression post-translation?
Cessation of protein folding
