Unit 4 lecture 2 part 1 11/9/22 Flashcards
Gene expression in bacteria is controlled by a mechanism described as the __________
Operon model
The regulatory “switch” is a segment of DNA called an __________ usually positioned within the __________
operator
promoter
An __________ is the entire stretch of DNA that includes the operator, the promoter, and the genes that they control
operon
The operon can be switched off by a __________
protein repressor
The __________ prevents gene transcription by binding to the __________ and blocking __________
repressor
operator
RNA polymerase
The repressor can be in an __________ or __________ form, depending on the presence of other molecules
active
inactive
A __________ is a molecule that cooperates with a repressor protein to switch an operon off
corepressor
When tryptophan is __________ , it binds to the trp repressor protein, which then turns the __________
present
operon off
A __________ is one that is usually on; binding of a repressor to the operator shuts off transcription
repressible operon
An __________ is one that is usually off; a molecule called an inducer inactivates the repressor and turns on transcription
inducible operon
The __________ is an inducible operon and contains genes that code for enzymes used in the hydrolysis and metabolism of __________
lac operon
lactose
A molecule called an __________ inactivates the repressor to turn the lac operon on
inducer
For the lac operon, the inducer is __________ , formed from lactose that enters the cell
allolactose
Enzymes of the lactose pathway are called __________
inducible enzymes
__________ usually function in __________ ; their synthesis is induced by a chemical signal
inducible enzymes
catabolic pathways
__________ usually function in __________ ; their synthesis is repressed by high levels of the end product
repressible enzymes
anabolic pathways
Regulation of the trp and lac operons involves __________ of genes because operons are switched off by the active form of the repressor
negative control
E. coli will preferentially use __________ when it is present in the environment
glucose
When glucose is scarce, __________ __________ acts as an activator of transcription
CAP(catabolite activator protein)
CAP is activated by binding with __________ __________
cyclic AMP(cAMP)
Activated CAP attaches to the __________ of the lac operon and increases the affinity of __________ , thus accelerating transcription
promoter
RNA polymerase
When glucose levels __________ , CAP detaches from the lac operon, and transcription proceeds at a very low rate, even if lactose is present
increase
In multicellular organisms, regulation of gene expression is essential for __________
cell specialization
Differences between cell types result from __________ __________ , the expression of different genes by cells with the same genome
differential gene expression
In all organisms, a common control point for gene expression is at __________
transcription
The structural organization of __________ packs DNA into a compact form and also helps regulate gene expression in several ways
chromatin
The location of a __________ relative to __________ and __________ or __________ attachment sites can influence gene transcription
gene promoter
nucleosomes
scaffold
lamina
Chemical modifications to __________ and __________ can influence chromatin structure and gene expression
histone proteins
DNA
In __________ __________ , acetyl groups are attached to positively charged lysines in histone tails
histone acetylation
The addition of __________ __________ can condense chromatin and lead to reduced transcription
methyl groups (methylation)
__________ is the addition of methyl groups to certain bases in DNA, usually __________
DNA methylation
cytosine
After replication, enzymes methylate the correct daughter strand so that the methylation pattern is __________
inherited
Though chromatin modifications __________ alter DNA sequence, they may be passed to future generations of cells
do not
The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called __________
epigenetic inheritance
__________ __________ provide initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery
Chromatin modifitying enzymes
