Final answer:
Positive control is the type of gene regulation where transcription occurs due to the stimulation by activator proteins. These activators bind to regulatory elements near gene promoters to initiate gene expression, which is crucial for organismal development and function.
Step-by-step explanation:
Positive control is a type of gene regulation in which transcription occurs only if a regulatory molecule stimulates transcription. This occurs when certain proteins, known as activators, bind to particular DNA sequences called regulatory elements near the promoters of genes. These activators are essential for helping the RNA polymerase bind to the promoter and start the transcription of specific genes. In contrast to positive control, there also exists negative control, where repressors bind to DNA and impede transcription. Gene expression is critical for the proper function and development of an organism. Errors in these regulatory mechanisms can lead to diseases such as cancer.
For example, the lac operon in prokaryotes is an instance of inducible control and it requires the presence of an inducer, lactose, to 'turn on' the transcription of genes necessary for lactose metabolism. On the other hand, the trp operon illustrates repressible control, where the presence of the amino acid tryptophan acts to 'turn off' the genes responsible for its own production.