Final answer:
A gene that codes for an enzyme is expressed when the cell synthesizes that particular enzyme. Gene expression involves transcription and translation, critical for protein synthesis, and is regulated according to the cell's requirements.
Step-by-step explanation:
A gene that codes for an enzyme is said to be expressed in a cell if the cell actually synthesizes the enzyme. Gene expression is a critical process that involves turning on a gene to produce RNA and protein. This process allows cells to create proteins and enzymes necessary for their function and is controlled by the cell's DNA. Enzymes like pyruvate carboxylase and beta-galactosidase are synthesized when a gene is expressed. These enzymes, whether inducible or constitutive, are vital for myriad cellular functions and metabolic pathways.
The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein, which encompasses the processes of replication, transcription, and translation. For a gene to be expressed, it must be transcribed into mRNA, which then directs the synthesis of proteins through translation. For proper cellular function, it is essential that these proteins are synthesized at the appropriate time and in the right quantity, which is regulated by internal chemical mechanisms within the cell.