Agglutination reactions are similar in principle to precipitation reactions they depend on the crosslinking of polyvalent antigens. Just as an excess of antibody inhibits precipitation reactions, such excess can also inhibit agglutination reactions; this inhibition is called the prozone effect.

TLS Online TPP Program

#Id: 6368

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 6369

#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: 6370

#Unit 2. Cellular Organization

Lac repressor binds as a tetramer to two operators.

TLS Online TPP Program

#Id: 6371

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 6372

#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: 6373

#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.