The promoters for Classes I and II, 5S and tRNA genes, are internal; they lie downstream of the start point.

TLS Online TPP Program

#Id: 2415

#Unit 3. Fundamental Processes

Rho-independent terminators, also called intrinsic terminators because they need no other factors to work, consist of two sequence elements: a short-inverted repeat (of 20 nucleotides) followed by a stretch of about eight A:T base pairs.

TLS Online TPP Program

#Id: 2416

#Unit 3. Fundamental Processes

Model of Intrinsic Termination

TLS Online TPP Program

#Id: 2417

#Unit 3. Fundamental Processes

Termination requires that all hydrogen bonds holding the RNA–DNA hybrid together must be broken, after which the DNA duplex reforms.

TLS Online TPP Program

#Id: 2418

#Unit 3. Fundamental Processes

he ability of the enzyme to terminate in vitro, however, is strongly influenced by parameters such as the ionic strength and temperature at which the reaction is performed.

TLS Online TPP Program

#Id: 2419

#Unit 3. Fundamental Processes

Termination depends on the RNA product and is not determined simply by scrutiny of the DNA sequence during transcription.

TLS Online TPP Program

#Id: 2420

#Unit 3. Fundamental Processes

Intrinsic terminators—that is, those that do not require auxiliary rho factor (r), as described shortly—require a GC–rich hairpin to form in the secondary structure of the RNA being transcribed.