Working model of the trp Operon

This is a working model of the trp operon.

To begin, the two DNA strands can be set up in cis (next to each other on the table) with the TrpR upstream (to the left in this case) of the trp operon.

The repressor protein should be slotted into the trpR gene.

• The trp Amino Acid should be slotted into the end of the structural genes.

RNA pol can then be slid from 3' to 5' (left to right) first creating the TrpR protein, (which will be inactive at this point) and then creating the trp Amino acid.

The trp Amino acid can then be slotted into either the repressor, to activate it, which will now be able to fix to the operator and block RNA pol, or it can be slotted into the leader sequence to represent attentuation.

My students have enjoyed using this model and it has done well to demonstrate the repressible nature of the trp operon.

Some limitations of the model:

Could lead to a misconception that RNA polymerase creates proteins.
It should be explained to students that transcription and translation occur simultaneously and that the ribosome is not represented here for simplicity, but the process of RNA pol transcribing the gene effectively results in a protein being made.

Could lead to a misconception about the Trp structural genes.
It does look a little like the trp structural genes are transcribed/translated into the trp Amino Acid. IT should be explained to students that trp is synthesised BY THE STRUCTURAL proteins which themselves are synthesised in this process. The creation of the trp skips this step.

• Attenuation is really cursory here.
  This model only really shows that the presence of trp interacts with the leader sequence to downregulate the expression of structural genes. GOOD LUCK modelling hairpin loops for high school students!

Print Settings

• Printer brand:

Prusa

• Printer:

I3 MK3S

• Rafts:

No

• Supports:

Doesn't Matter

• Resolution:

0.3 mm

• Infill:

20%

• Filament brand:

Filoform

• Filament material:

PLA

• Notes:

I didn't print this with supports, but if the cooling isn't up to scratch on your printer you may need supports for the holes where the trp can be inserted.

The stl is oriented so that supports are not necessary. If you do autogenerate supports with appropriate settings, it won't add much time anyway, and will ensure everything works.