The action of Dicer generates the short RNA molecule that will determine what target RNA is acted upon. The active form of the regulatory RNA is the single-strand form—at this stage called the guide RNA—incorporated into a RISC protein complex.

TLS Online TPP Program

#Id: 559

#Unit 2. Cellular Organization

The O1 operator extends from position -5 just upstream of the mRNA start point to position +21 within the transcription unit.

TLS Online TPP Program

#Id: 560

#Unit 2. Cellular Organization

When polymerase binding causes transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level. 

Binding of RNA polymerase is the rate-limiting step in this case.

TLS Online TPP Program

#Id: 561

#Unit 2. Cellular Organization

lacZ encodes for b-galactosidase, a tetramer of 500 kD. The enzyme breaks lactose is cleaved into glucose and galactose. This enzyme also produces an important byproduct, b-1,6-allolactase.

TLS Online TPP Program

#Id: 562

#Unit 2. Cellular Organization

The lac mRNA (as most mRNA is in bacteria) is extremely unstable and decays with a half-life of only 3 minutes.

TLS Online TPP Program

#Id: 563

#Unit 2. Cellular Organization

B-1,6-allolactase is a true inducer of Lac operon which activates Lac ZYA gene expression by inhibiting Lac Repressor

TLS Online TPP Program

#Id: 564

#Unit 2. Cellular Organization

Negative Regulation/ Positive Regulation or catabolic repression