Constitutieve en regulerende genen

Constitutive or housekeeping genes are continuously expressed for essential functions like glycolysis, ribosome assembly, and DNA replication.

Regulated genes are expressed only under specific conditions to suit varying cell requirements.

Specific substrates induce gene expression, as seen in lactose metabolism in E. coli.

Contrastingly, repressible genes are turned off when their products are abundant, preventing unnecessary synthesis of molecules like amino acids.

Transcriptional regulation mechanisms — induction and repression — involve regulatory proteins and RNA molecules that control mRNA synthesis.

Repressors inhibit transcription by binding to DNA regions called operators, preventing transcription.

In contrast, activators enhance transcription by binding to promoter regions and facilitating RNA polymerase attachment.

Lastly, the attenuation controls gene expression by coupling transcription and translation. It relies on forming alternative secondary structures like stem-loops in the mRNA to terminate transcription prematurely in response to environmental or metabolic signals, like the availability of certain amino acids.