Biol 3130 Lecture 10: Control of Gene Expression in Prokaryotes - The Lac Operon

These flashcards cover key terms and concepts related to the Lac operon and gene expression control in prokaryotes.

Lac Operon

A group of genes and their regulatory elements that control lactose metabolism in E. coli.

lacI

A gene that encodes the repressor protein which binds to the operator to block transcription.

Permease

A protein that facilitates the entry of lactose into the bacterial cell.

β-Galactosidase

An enzyme encoded by the lacZ gene that breaks down lactose into glucose and galactose.

Allolactose

An inducer molecule that binds the repressor protein to allow transcription of the lac operon.

Negative Control

Regulation where a repressor protein inhibits transcription in the absence of lactose.

Positive Control

Regulation where an activator protein enhances transcription in response to cAMP binding.

Catabolite Activator Protein (CAP)

A protein that, when activated by cAMP, enhances transcription of the lac operon.

Constitutive Expression

Continuous expression of a gene regardless of the presence or absence of an inducer.

Cis-acting Mutation

A mutation that affects the same DNA molecule on which it resides.

Trans-acting Mutation

A mutation that affects the expression of genes located on the same or different DNA molecules.

Haploid

Having a single set of chromosomes, typical of most prokaryotes.

Diploid

Having two sets of chromosomes, typical of somatic cells in eukaryotes.

Partial Diploid

A cell containing one complete set of chromosomes and an extra segment of DNA, such as an F plasmid containing the lac operon.

Repressor

A protein that binds to the operator to prevent transcription of the operon.

Inducer

A molecule that triggers the expression of a gene by inhibiting the repressor.

Transacetylase

Enzyme encoded by the lacA gene, involved in the metabolism of lactose.

Operator

A DNA sequence where the repressor binds to prevent transcription.

Promoter

A DNA sequence where RNA polymerase binds to initiate transcription.

Structural Genes

Genes that encode proteins responsible for the operon's function.