Gene Expression Flashcards
Human fingers are originally webbed when they first develop. How does the body create individual fingers from this webbed structure?
The cells of the webbing undergo apoptosis: they shrink in size, their nuclear DNA is degraded, and they separate into small, membrane-wrapped fragments. Finally, nearby phagocytic cells engulf these pieces.
Defined as programmed cell death
Apoptosis is defined as programmed cell death, by which a damaged cell initiates an intracellular cascade resulting in destruction of the cell.
Genetic system used by prokaryotes to regulate expression of specific genes
Operon
Positive control operon
Gene expressed when an activator is present (prok)
Negative control operon
Genes expressed unless repressor is present (prok)
True or False: The lac and trp operons are both negatively controlled operons
True, both are under negative
What are the subtypes of negative operons?
Inducible and Repressible
This type of operon requires an activator
positively controlled gene
This type of operon requires a repressor
negatively controlled gene
Specific operon whose normal position is the off position
Lac operon which is a negative inducible
Specific operon whose default is the on position
trp operon which is negative repressible
True or False: the lac operon is under negative inducible control as well as positive control
True
What are the components to the Lac operon?
The lac operon has a
- promoter site
- CAP binding site
- operator
- LAC Z,Y,A
Describe how the Lac operon works
The lac operon is influenced by both negative and positive control. The operon possesses genes that help with lactose metabolism. The preferred sugar is glucose but when glucose is not as available, the prokaryote has means of metabolizing lactose which is where the lac operon comes into play.
In terms of NEGATIVE control, it is an INDUCIBLE negative operon. THe repressor is normally bound to the operator until ALLOLACTOSE binds to the repressor releasing it from the site.
In terms of POSITIVE control, there is the CAP binding site. WHen clucose is low, cAMP is high. cAMP binds to CAP (catabolyte activator protein) which binds to the CAP binding site which helps increase transcription
True or False: When lactose levels are low and glucose levels are high, the repressor is not bound to the lac operon
False, it is bound
True or False: when tryptophan is abundant, the trp operon is turned off
true
True or False: tryptophan exhibits positive control on its operon
false, negative
Short sequence upstream of its target gene that contains a TATA box
Eukaryotic promoter sequence
Proteins that recruit RNA polymerase
Mediator porteins
Proteins that bind to pseific DNA sequences to regulate gene expression
Transcription factors
Enhancer
EUKS! sequences that promote expression, can be upstream or downstream. Activators bind to them. Enhancer region gets close to promoter sequence by a DNA hairpin loop to facilitate the imitation of transcription
Silencer
EUKS! Repressor binds to these
Acetylation
Helps make DNA more accessible for transcription by masking positive charges on histones
Deacetylation
Promote tighter packing of DNA
Methylation
Methyl group added to cytosine or adening nucleotides in DNA. It silences gene sequences. Plays a role in epigenetics
Heritable changes that affect gene expression with out directly changing the sequences itself
Epigenetics
siRNA
small interfering is double stranded
microRNA
single stranded
RISC
RNA induced silencing complex
An individual is experiencing symptoms related to the lack of a specific protein. However, genetic analysis finds no mutation in the gene encoding this protein. If a mutation does indeed exist, it would most likely be found:
A mutation in the promoter sequence would prevent initiation of transcription entirely, resulting in a total lack of the relevant protein.
