Switch the operons on and off

Exercise and reference answers

Questions

1. Statement is true

   Yes

   Statement

   The lac operon is transcribed only when glucose is absent and lactose is present.

2. Statement is true

   Yes

   Statement

   Two tryptophan molecules bind the trp repressor before it can sit on the operator.

3. Statement is true

   No

   Statement

   The trp operon stays switched on while tryptophan is plentiful in the cell.

4. Statement is true

   Yes

   Statement

   Levels of cyclic AMP in E. coli rise as the supply of glucose runs low.

5. Statement is true

   No

   Statement

   Inducers are proteins that always increase the transcription of an operon.

6. Statement is true

   Yes

   Statement

   All the genes needed to use lactose sit next to each other in one operon.

Instructions

Tap true or false for each statement about how bacteria control their operons.

Explanation