-
Operon
- Set of structural genes with related functions that share a common promoter
- Genes are controlled by shared promoter
- Genes are transcribed together and produce a single mRNA
-
Regulator gene
- Binds the operator in the operon of the structural genes
- Has its own promoter
- Encodes a protein that regulates transcription not considered an actual part of the operon, but it affects the operon function
-
Structural genes
- Encode proteins that are used in metabolism or biosynthesis
- Also includes those that encode proteins that play a structural role in the cell
-
Regulatory genes
- Genes whose products interact with other sequences and affect the transcription or translation of those sequences
- Products: RNA or proteins
-
DNA binding proteins
- Part of regulatory genes
- Specialized proteins that bind to DNA sequences and affect their expression
- They have special motifs that facilitate binding to and altering DNA
-
lac operon
- An operon required for the transport and metabolism of lactose in E. coli
- Consists of three structural genes: lacZ, lacY, lacA(i)
-
Structure of the lac operon
- The lac operon consists of three structural genes, a promoter, a terminator, regulator, and an operator
- Transcription of all genes starts with the binding of the enzyme RNA polymerase, a DNA binding protein, which binds to a specific DNA binding site, the promoter, upstream of the genes
-
Regulatory elements
- Sequences that are not transcribed but affect expression of sequences to which they are linked
- Not actually a gene
-
Absence of lactose
The repressor protein encoded binds to the lac operator and prevents transcription
-
|
|
