Some of the cytochrome b6 f complexes are found in the stroma region of the membrane, where photosystem I is located. Under certain conditions cyclic electron flow from the reducing side of photosystem I, through the b6 f complex and back to P700, is known to occur.

TLS Online TPP Program

#Id: 2645

#Unit 13. Methods in Biology

In G-less cassette transcription, a promoter is fused to a double stranded DNA cassette lacking G’s in the nontemplate strand, then the construct is transcribed in vitro in the absence of GTP. 

TLS Online TPP Program

#Id: 2646

#Unit 13. Methods in Biology

A G-less cassette, or stretch of nucleotides lacking guanines in the nontemplate strand, is inserted just downstream of the promoter. This template is transcribed in vitro with CTP, ATP, and UTP, one of which is labeled, but no GTP.

TLS Online TPP Program

#Id: 2647

#Unit 13. Methods in Biology

In G-less cassette, transcription will stop at the end of the cassette where the first G is required, yielding an aborted transcript of predictable size (based on the size of the G-less cassette, which is usually a few hundred base pairs long).

TLS Online TPP Program

#Id: 2648

#Unit 13. Methods in Biology

Primer extension, S1 mapping, and Northern blotting are useful for determining the concentrations of specific transcripts in a cell at a given time, but they do not necessarily tell us the rates of synthesis of the transcripts.

TLS Online TPP Program

#Id: 2735

#Unit 13. Methods in Biology

In Run-on transcription- the RNA polymerase that has already initiated transcription in vivo simply “runs on” or continues to elongate the same RNA chains. 

TLS Online TPP Program

#Id: 2736

#Unit 13. Methods in Biology

The run-on reaction is usually done in the presence of labeled nucleotides so the products will be labeled.