Gene Regulation in Bacteria

Flashcards on Gene Regulation in Bacteria

Gene expression

The process by which information contained in genes is decoded to produce other molecules that determine the phenotypic traits of organisms

Promoter

Nucleotide sequence, 20–200 bp long, that is the initial binding site of RNA polymerase and transcription initiation factors.

Promoter

The DNA sequence in a gene to which RNA polymerase binds to initiate transcription.

Upstream and downstream

Terms describing directions or positions with respect to a gene. Upstream signifies the direction opposite to that traveled by RNA polymerase as it transcribes the gene, while the downstream direction is the direction in which RNA polymerase moves during transcription.

Sigma factor

Increases the affinity of the RNA Polymerase to the promoter

Cistron

DNA sequence that encodes a single polypeptide chain.

Polycistronic mRNA

mRNA molecules contain information for the amino acid sequences of several different proteins.

Negative regulation

The default state of transcription is “on” until it is turned “off” by a repressor protein that binds to the DNA upstream from the transcriptional start site.

Positive regulation

The default state of transcription is “off” until turned “on” by the binding of a transcription activator protein

Transcription factor

A protein that binds DNA sequence-specifically and regulates transcription.

Operon

A unit of DNA composed of specific structural genes (encoding functional products), plus a promoter and an operator. These elements work in unison to regulate the coordinated response of expression of the structural genes to environmental changes.

Lactose-utilization system

Structural genes (lacZ and lacY), which encode proteins needed for the transport and metabolism of lactose and regulatory elements (the repressor gene lacI, the promoter lacP, and the operator lacO).

Repressor

The product of the lacI gene, which binds to a unique sequence of DNA bases constituting the operator.

Inducer

Binds to the repressor which changes the shape of the repressor

Trans-acting

Describes the action of a protein or RNA that can bind to target sites on any DNA or RNA in the cell; a protein or RNA that acts in trans is said to be trans-acting. Molecules that act in trans diffuse throughout the cell to find their target sites.

Cis-acting

Describes the action of a DNA site or a region in an RNA molecule that acts only on the DNA or RNA of which it is a part; a DNA site or an RNA that acts in cis is said to be cis-acting.