Topic 7-3 Flashcards
the process by which a gene creates a “gene product” (ex: proteins, RNA) that have cellular/organismal functions
gene expression
mechanisms that have evolved to control gene expression, controlling the flow of information
gene regulation
provides the molecular basis for the relationship between genotype and phenotype
gene expression
encoding products that interact with other sequences and affect the transcription and translation of these sequences
regulatory genes
DNA sequences that are not transcribed but play a role in regulating other nucleotide sequences
regulatory elements
encoding proteins
structural genes
continuously expressed under normal cellular conditions
constitutive expression
in bacteria, gene regulation maintains internal ________, turning genes on and off in response to _________.
flexibility, environmental changes
in multicellular eukaryotic organisms, gene regulation also brings about __________.
cell differentiation
transcription in bacterial cells is regulated by:
operons
is composed of a promoter + additional sequences that control transcription (operator) + structural genes
operon
a DNA sequence which encodes products that affect the operon function but are not part of the operon
regulator gene
inducible and repressible operons
negative and positive controls
list two examples of operons in E.coli
- the lac operon
- the trp operon
used classical genetics to uncover the”operon model” of how bacteria regulate genes
Francois Jacob and Jacques Monod
operons allow the cell to coordinate:
expression of multiple gene products with one promoter
usually, the structural genes in an operon have:
a related function
DNA binding proteins that can bind to DNA in the operon to regulate transcription either negatively (repressors) or positively (activators)
regulatory proteins
repressors bind operators and blocks RNA pol. and transcription
negative control
activator ususally do not bind operators, and frequently bind to promoters and facilitate RNA pol. binding and transcription
positive control
proteins that change shape and function upon binding other proteins
allosteric proteins
transcription is usually off and needs to be turned on
inducible operon
transcription is normally on and needs to be turned off
repressible operons
the control at the operator site is negative. molecule binding is to the operator inhibiting transcription. such operson are usually off and need to be turned on.
negative inducible operons
a small molecule (allosteric modulator) that turns on transcription
inducer
the control at the operator site is negative. but such transcription is usually on and needs to be turned off
negative repressible operons
a small molecule (allosteric modulator) that binds to the repressor and makes it capable of binding to the operator to turn off transcription
co-repressor
- the inducer is a precursor for enzymes produced by the operon, thus transcription itself leads to more enzymes and effects levels of inducer
- feedback system allowsbacteria to adapt to their environment and function more economically
- some genes are only made if the precursor/inducer is present (less wasteful production of enzymers)
these are characteristics of:
a negative inducible operon
- a negative inducible operon
- invovled in lactose metabolism
- inducer: allolactose
these are characteristics of:
the lac operon
what is the lac operon repressor encoding gene?
lacI
what is the lac operon promoter?
lacP
what is the lac operon operator?
lacO
what are the encoding beta-galactosidases of the lac operon?
lacZ
what is the encoding permease of the lac operon?
lac Y
what is the encoding transacetylase of the lac operon?
lacA
true or false: the repression of the lac operon completely shuts down transcription
false
bacterial cells utilize the lac operon to respond to changing ________ levels in the environment by efficiently switching on and off _________.
glucose/lactose, lactose metabolism
what is the preferred energy source for E.coli?
glucose
can be used as energy for E.coli if it is broken down via catabolism
lactose
catabloizes lactose into galactose into glucose, or into allolactose
beta galactosidase
allolactose acts as an _______
inducer
an activator protein that binds just upstream of the lac operon promoter and promotes transcription. requires binding to cAMP to bind the DNA
catabolite activator protein (CAP)
occurs where in a high concentration fo the catabolite, transcription is repressed
catabolite repression
CAP is an example of ________ of an operon
positive control
Jacob and Monod used ______ strains of bacteria that contain plasmid F (which would carry a second copy of the lac operon that they could mutatue).with different combinations of mutations in the bacterial genome adn plasmid F, they could determind if mutations had a ________ of ________ effect on lactose metabolism
partial-diploid, dominant, recessive
a situation where a gene on a separate piece of DNA affects the transcription of another gene.
trans-acting factor
a situation where one gene will affect the transcription of another gene on the same strand of DNA
cis-acting factor
lacZ, lacY - mutations affected amounts of beta-galactosidase or permease independently
structural mutations
mutations in lacI affect both beta-galactosidase and permease levels
regulator gene mutations
some mutations in lacI resulted in lac proteins being produced all the time regardless of lactose levels. this is called a:
constitutive mutant
if mutations occured in only one copy of lacI (either plasmid or genome), both lac operons functioned normally. this indicated that the lacI+ gene was:
- dominant over the lacI- gene
- lacI was a trans-acting factor (encodes regulatory protein)
some constitutive mutations of lac proteins were evident only if the structual genes on the same DNA (plasmid or genome) were not mutated. these mutations were found to be in the _______ and prevent the binding of the regulator protein –> thus are ________ elements. overall this is a ________ mutation.
lacO operator, cis-regulating, operator gene
