Three major classes of animal-cell junctions: 

1. Anchoring junctions

2. Tight junctions

3. Gap junctions

TLS Online TPP Program

#Id: 3267

#Unit 3. Fundamental Processes

Bruce Ames of the University of California at Berkeley devised a simple test for the potential carcinogenic effects of chemicals based on their capacity to cause mutations in the bacterium Salmonella typhimurium.

TLS Online TPP Program

#Id: 3268

#Unit 3. Fundamental Processes

The Ames test uses a strain of S. typhimurium that is mutant for the operon responsible for the biosynthesis of the amino acid histidine. For example, the mutant operon might contain a missense or a frameshift mutation in one of the genes for histidine biosynthesis.

TLS Online TPP Program

#Id: 3271

#Unit 3. Fundamental Processes

Chemicals that are found to be mutagenic in the Ames test can then be tested for their potential carcinogenic effects in animals.

TLS Online TPP Program

#Id: 3272

#Unit 3. Fundamental Processes

Mismatch Repair Correction of the rare mismatches left after replication in E. coli improves the overall fidelity of replication by an additional factor of 10^2 to 10^3.

TLS Online TPP Program

#Id: 3273

#Unit 3. Fundamental Processes

The mismatch repair system of E. coli includes at least 12 protein components (Table) that function either in strand discrimination or in the repair process itself.

TLS Online TPP Program

#Id: 3277

#Unit 3. Fundamental Processes

Methylation of DNA strands can serve to distinguish parent (template) strands from newly synthesized strands in E. coli DNA