Final answer:
The constantly transcribed genes in bacteria that code for proteins always necessary for survival are called constitutive genes or housekeeping genes. These genes are responsible for essential cellular functions and are expressed continuously, as opposed to being regulated by environmental stimuli.
Step-by-step explanation:
The type of gene that is constantly transcribed in bacteria because the proteins they code for are always needed are called constitutive genes or housekeeping genes. These genes encode enzymes that are crucial for housekeeping functions, which include DNA replication, repair, and expression, as well as essential metabolic processes. Unlike inducible or repressible genes which are only expressed in response to certain environmental stimuli, constitutive genes are transcribed and translated continuously to sustain consistent intermediate levels of the protein products indispensable for cellular maintenance.
Bacteria rely on a streamlined and efficient way to regulate the production of these proteins through the organization of genes into operons. Operons allow for the coordinated control of gene expression. The regulation of an operon could be achieved by inducible control, repressible control, or activator control mechanisms. However, constitutive operons are not influenced by such regulatory controls and are expressed continuously.
Therefore, when answering a test question such as 'An operon encoding genes that are transcribed and translated continuously to provide the cell with constant intermediate levels of the protein products is said to be which of the following?', the correct answer would be C. constitutive.