Chp 12

Negative control of transcription

Involves repressor proteins binding to DNA sequences, inhibiting gene transcription.

Positive control of transcription

Involves activator proteins binding to DNA sequences, promoting gene transcription.

Repressor proteins

Regulatory proteins that exert negative control of transcription by binding to DNA and obstructing RNA polymerase.

DNA-binding domain

A specific protein region that directly interacts with DNA to bind to a specific sequence.

Allosteric domain

A site on a protein that, when bound by a molecule, induces conformational changes in another part of the protein, affecting its function.

Repressible operon

A group of genes that are usually on, but can be turned off in response to environmental conditions.

Attenuation

A regulatory mechanism that can prevent the transcription of certain genes in response to environmental conditions.

lac operon structural genes

Includes lacZ (encodes beta-galactosidase), lacY (encodes lactose permease), and lacA (encodes beta-galactoside transacetylase).

Function of lac operon when lactose is absent

The lac repressor binds to the operator, preventing transcription of the operon.

Function of lac operon when lactose is present

Lactose or allolactose binds to the lac repressor, causing its release from the operator, allowing transcription.

Genotype of a partial diploid example

F' I+ P+ O+ Z+ Y- / I+ P+ O+ Z- Y+, where '+' indicates a wild type gene and '-' indicates a mutant.

3-4 stem loop of mRNA

The termination stem loop involved in the regulation of transcription termination.

2-3 stem loop of mRNA

The antitermination stem loop that prevents transcription termination.

1-2 stem loop of mRNA

Can induce a pause in the attenuation process.