Termination:

Transcription   continues   until a termination   sequence   is reached.   The most general termination signal is a GC-rich region which is a palindrome, followed through an AT-rich sequence. The RNA made from the DNA palindrome is self- complementary and so base pairs internally to form a hairpin structure rich in GC base pairs followed through four or more U residues shown in the figure. However, not all termination sites have this hairpin structure.  Those which lack such a structure need an additional protein, called rho (p), to help recognize the termination site and stop transcription.