Bergmann’s rule: populations in colder climates tend to have greater body mass than those

in warmer climates. This pattern is so common that it has a name.

TLS Online TPP Program

#Id: 6375

#Unit 2. Cellular Organization

Molecules that induce enzyme synthesis but are not metabolized are called gratuitous inducers such as IPTG

TLS Online TPP Program

#Id: 6376

#Unit 2. Cellular Organization

IPTG (isopropyl b-D-1-thiogalactopyranoside) 

X-gal (5-bromo4-chloro-3-indolyl-b-D-galactopyranoside). When acted on by that enzyme, X-gal releases a blue color that makes it useful as substrate in assays.

TLS Online TPP Program

#Id: 6377

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 6378

#Unit 2. Cellular Organization

The lac operon has three paradoxes

if the operon is in a repressed state, how does the inducer enter the cell to start the process of induction

 If the operon is in a repressed state, how Repressor is removed with allolactose 

 How is allolactose synthesized in Repressed state Answer is Leaky Expression

TLS Online TPP Program

#Id: 6379

#Unit 2. Cellular Organization

Leaky Expression

In repressed state, an occasional transcript gets made. This happens because every so often, RNA polymerase will manage to bind the promoter in place of the Lac repressor. This leakiness encode meager level of Z, Y and A.

TLS Online TPP Program

#Id: 6380

#Unit 2. Cellular Organization

OC are constitutive because repressor protein is unable to bind; this allows RNA polymerase to have unrestrained access to the promoter.  The Oc mutations are cis-acting/cis dominant, because they affect only the contiguous set of structural genes.