You have isolated two mutations that show decreased expression of the Lac operon. However, unlike like the promoter mutations, these mutations don’t respond to the inducer IPTG. These mutations, designated Lac3– and Lac4–, are evaluated for the quantity of ß-galactosidase and permease activity expressed with or without IPTG:

 

Mapping experiments reveal that Lac3– and Lac4– are different short deletions located in the region before the start of the LacZ gene. Given the data shown above suggest which genetic element(s) in addition to part of the promoter has been deleted in each mutant. 

#Question id: 2829

#Unit 2. Cellular Organization

Scaffold-associated regions

a. are the chromosome attachment points for the mitotic spindle.

b. can insulate transcription units from each other.

c. are the points at which DNA interacts with histone proteins.

d. are found between transcription units.

#Question id: 2830

#Unit 2. Cellular Organization

#Question id: 2831

#Unit 2. Cellular Organization

Specific DNA control elements in promoters can

a. interact with general transcription factors.

b. interact with repressor proteins.                 

c. interact with activator proteins.

d. remain unavailable because of condensed chromatin. 

#Question id: 2832

#Unit 2. Cellular Organization

Reporter genes are used to

a. express enzymes that are not easily assayed in cell extracts.

b. express enzymes that are easily assayed in cell extracts.

c. characterize DNA control elements.                     

d. characterize reporter plasmids.

#Question id: 2835

#Unit 2. Cellular Organization

An enhancer

a. can be located upstream of a promoter.

b. can be located downstream of a promoter.

c. can be located a variable distance from the promoter.

d. is always located within 1 kb of the promoter.

e. can be cell-type-specific.

#Question id: 2836

#Unit 2. Cellular Organization