The promoter of the araBAD operon from E. coli is activated in the presence of arabinose and the absence of glucose and directs expression of genes encoding enzymes required for arabinose metabolism. 

Unlike the cases of lac and gal genes, where a repressor and an activator work together, here two activators work together: AraC and CAP. 

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#Unit 3. Fundamental Processes

GlnRS is absent in gram-positive bacteria, archaebacteria, cyanobacteria, mitochondria, and chloroplasts.

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#Id: 4765

#Unit 5. Developmental Biology

 PIE -1, is necessary for germline cell fate.

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#Id: 2237

#Unit 11. Evolution and Behavior

Neutral selection (Ka/Ks = 1)

Positive selection (Ka/Ks > 1)

Purifying selection (Ka/Ks < 1)

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#Unit 8. Inheritance Biology

Unbalanced gene dosage leads to developmental abnormalities.

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#Id: 3117

#Unit 3. Fundamental Processes

The origin of E. coli, oriC, is 245 bp in length. The genome of E. coli is replicated bidirectionally from a single unique site called the origin, identified as the genetic locus oriC.

Two replication forks initiate atoriCand move around the genome at approximately the same speed to a special termination region.