BIO 235 Exam 4 UPDATED Exam
Questions and CORRECT Answers
Induction (gene regulation) example in E. coli - CORRECT ANSWER - E. coli digests
lactose but does not have many genes that incorporate lactose into the environment bc there is
not a lot of lactose
When enzymes break down lactose, they signal the cell to express more genes that express the
enzymes and permeases for the gene
The more lactose you have, the more the genes will express
Eventually, it will break down all of the lactose to the point where the cell no longer expresses
the genes to break down lactose
Operon theory - CORRECT ANSWER - one signal can simultaneously regulate expression
of several clustered genes
Lactose operon in E. coli - CORRECT ANSWER - Structural genes (lacZ, lacY, lacA) -
something that does something
Promoter - site of which RNA polymerase binds
Operator - controls transcription initiation
Repressor - binds to operator (encoded by lacI gene, Trans-acting)
Inducer - prevents repressor from binding to operator
Negative regulator - CORRECT ANSWER - protein that prevents transcription
Repression of lac gene expression - CORRECT ANSWER - lacI repressor gene makes
repressor protein, which binds to the operator to stop transcription
When it binds to the operator, it is turned off and no transcription occurs
regulatory elements - CORRECT ANSWER - short DNA sequences that affect the binding
of RNA polymerase to the promoter
, operator
How does the presence of lactose affect repressor protein? - CORRECT ANSWER - When
lactose is presence, allolactose (inducer) is made, which binds to the repressor. This changes its
shape and prevents it from binding to the operator. RNA polymerase is able to bind to the
promoter and initiate transcription.
Allosteric protein - CORRECT ANSWER - Protein that changes its conformation on
binding with another molecule.
constitutive expression - CORRECT ANSWER - gene product made continuously
constitutive mutants - CORRECT ANSWER - express the enzymes in the absence and
presence of inducer
lacI- mutant - CORRECT ANSWER - lac genes are expressed in the absence and the
presence of the inducer
The mutant repressor cannot bind to the operator, so enzymes are produced constitutively
lacIs mutants - CORRECT ANSWER - superrepressor binds to operator but cannot bind to
the inducer
repressor binds to operon, even when inducers are present
lac repressor domains - CORRECT ANSWER - DNA-binding domain
Inducer-binding domain
lacOc mutants - CORRECT ANSWER - have mutant operator that cannot bind to the
repressor
this causes genes expression in the absence and presence of the inducer (constitutive expression)
Questions and CORRECT Answers
Induction (gene regulation) example in E. coli - CORRECT ANSWER - E. coli digests
lactose but does not have many genes that incorporate lactose into the environment bc there is
not a lot of lactose
When enzymes break down lactose, they signal the cell to express more genes that express the
enzymes and permeases for the gene
The more lactose you have, the more the genes will express
Eventually, it will break down all of the lactose to the point where the cell no longer expresses
the genes to break down lactose
Operon theory - CORRECT ANSWER - one signal can simultaneously regulate expression
of several clustered genes
Lactose operon in E. coli - CORRECT ANSWER - Structural genes (lacZ, lacY, lacA) -
something that does something
Promoter - site of which RNA polymerase binds
Operator - controls transcription initiation
Repressor - binds to operator (encoded by lacI gene, Trans-acting)
Inducer - prevents repressor from binding to operator
Negative regulator - CORRECT ANSWER - protein that prevents transcription
Repression of lac gene expression - CORRECT ANSWER - lacI repressor gene makes
repressor protein, which binds to the operator to stop transcription
When it binds to the operator, it is turned off and no transcription occurs
regulatory elements - CORRECT ANSWER - short DNA sequences that affect the binding
of RNA polymerase to the promoter
, operator
How does the presence of lactose affect repressor protein? - CORRECT ANSWER - When
lactose is presence, allolactose (inducer) is made, which binds to the repressor. This changes its
shape and prevents it from binding to the operator. RNA polymerase is able to bind to the
promoter and initiate transcription.
Allosteric protein - CORRECT ANSWER - Protein that changes its conformation on
binding with another molecule.
constitutive expression - CORRECT ANSWER - gene product made continuously
constitutive mutants - CORRECT ANSWER - express the enzymes in the absence and
presence of inducer
lacI- mutant - CORRECT ANSWER - lac genes are expressed in the absence and the
presence of the inducer
The mutant repressor cannot bind to the operator, so enzymes are produced constitutively
lacIs mutants - CORRECT ANSWER - superrepressor binds to operator but cannot bind to
the inducer
repressor binds to operon, even when inducers are present
lac repressor domains - CORRECT ANSWER - DNA-binding domain
Inducer-binding domain
lacOc mutants - CORRECT ANSWER - have mutant operator that cannot bind to the
repressor
this causes genes expression in the absence and presence of the inducer (constitutive expression)
