Do I or Do I Not Express B-Galactosidase?

By A.K. Matai

The lac operon has been covered in another post along with the possible scenarios you could encounter. But what happens to B-galactosidase expression, permease expression and trans-acetylase expression if you have an extrachromosomal F’ factor episome that carries another lac operon? Well, not to fear! I will guide you through a sample problem giving you a systemic method to solve these types of problems.

Sample Problem

In the E.coli strains below, the lac operon is present on both the chromosome and the extrachromosomal F’ factor episome. Each strain is growing on a specific media. Complete the table below by indicating the level of expression. The options are: 100% (full expression), 10-20% (partial expression), 1% (low expression) and 0% (no expression).

Do I or Do I Not Express B-Galactosidase SampleProblemLacOperonEdited.jpg

Weekly Tip to Succeed 

Practice, Practice and Practice!! Use this method or another method to solve problems that are similar to this. That way, when you see a problem like this, you’ll be able to solve it in no time.

Questions, Comments or Concerns?

Feel free to post a comment down below! I am happy to explain or expand on anything I have written in this post.


Bainscou. Next generation sequencing slide. Web. 12 Jan. 2017.


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