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32 Cards in this Set

  • Front
  • Back

Enzyme encoded by lacZ gene

Glucose and galactose products

Enzyme cleaves broad range of galactosides

Structural genes of lac operon

Encode for the primary structure of the enzymes/proteins

lac Z, lac Y, and lac A

Lac I

constitutive promoter and is expressed separately from the lac operon

Encodes lac repressor - low level of expression


RNA polymerase that can transcribe any gene that has a functional promoter


Regulatory proteins that decrease the level of transcripts for certain genes


Proteins that increase transcription

Regulatory sequences

Specific DNA regions to which regulatory proteins bind (kb)

Operator sites

sequences recognized by regulators in bacteria

Eukaryotic Vs Prokaryotic

E. genes are more often controlled by distal regulatory sequences

Locus control regions

Found in more complex eukaryotes

Enhancer and insulator elements

Several proteins bind to and activate gene transcription

DNA looping

May bring the bound proteins to the promoter and encourage assembly of the transcription initiation complex

Regulatory proteins

Have a DNA binding domain that recognizes a specific sequence

Often modular

Aid in oligomerization

Activate or repress transcription

Interact with other regulators

Allosteric effectors

Small molecules that can bind directly to the regulatory proteins and change their conformation


Helix turn helix

common and found in many protein folds. First helix and recognition helix fits in the major groove

Many are dimers with the recognition helices spaced 3.4 nm apart to fit neighboring grooves

Recognition helices

In helix turn helix proteins read the DNA sequence through interactions with the base pairs



is a monomeric helix turn helix

Zinc finger

Prominent part of many DNA binding folds

Interacts with the two cysteines and two histidines

Insert its alpha helix into the minor groove

Most common DNA binding domains in the human genome


alpha helices that wind around each other form part of some DNA binding domains

Basic region leucine zipper proteins

have long alpha helices of about 60 amino acids

The two helices have hydrophobic leucing residues on the surfaces that "zip" together

Basic region helix loop helix proteins

Have a coiled coil and a helix that fits in the major groove

Have four helices joined by a loop. The region where the four helices interact is the Four Helix Bundle


Made of beta sheets and connecting loops

Trp repressor

Helix turn helix protein

Depends on the level of tryptophan in the cell

When tryptophan levels are high, binds to operator and blocks RNA polymerase from binding

RNA polymerase + promoter

Activate transcription

Catabolite activator protein

Activates more than 100 E. coli promoters when carbon sources are low

Glucose depletion

Increases cAMP levels - this binds to CAP and increases its binding to DNA


enhances RNA polymerase by binding to the CTD

Class I: binds upstream of promoter

Class II: the CAP binding site overlaps the RNA polymerase binding site

CAP and Lac I

Regulate the lac operon

Lac operon

Responds to low glucose levels in the cell by allowing it to metabolize lactose instead if present

In low glucose, lactose available

CAP binds to the CAP operator, enhancing transcription STRONGLY ON

In high glucose, lactose available

Cap does not bind to the CAP operator, the lac repressor is not bound, WEAK transcription


Activates genes that are important for nitrogen metabolism

Binds at enhancer elements and activates transcription when phosphorylated


Stimulates its rate of ATP hydrolysis, which helps promote formation of the open complex