What is a terminator in DNA?

• A. A sequence of nitrogen bases that signals RNA polymerase to stop transcription
• B. A protein that ends translation
• C. A sequence that initiates replication
• D. A sequence that codes for RNA

Answer: (A)

A terminator is a DNA sequence that marks the end of a transcription unit by signaling RNA polymerase to stop transcription and release the RNA. In bacteria this can happen in two main ways: a rho-dependent mechanism where the Rho protein catches up to the polymerase, causing it to dissociate, or a rho-independent mechanism where a GC-rich hairpin in the RNA followed by a string of uracils destabilizes the transcription complex and promotes termination. This concept is about stopping transcription, not about translating a protein or starting DNA replication. It’s also not simply a sequence that codes for RNA; the terminator’s role is to halt transcription, though it is transcribed itself as part of the RNA product in some cases.