Operons and Gene Regulation Explained For Beginners

An operon is a group of genes that transcribe a single mRNA. The structure of an operon can be remembered using the acronym PROG, which stands for Promoter, Repressor Operator and the Genes. At the very end of this structure there is a termination sequence, which terminates transcription. Usually upstream from the operon is a regulatory gene encoding for a repressor which can bind to the operator. RNA polymerase is responsible for transcribing the genes of the operon.

The promoter is where the RNA polymerase binds to initiate transcription of the genes. The operator can be thought of as a stop light that either allows or prevents transcription of the genes by RNA polymerase. This depends on if the repressor is bound to the operator or not. If the repressor is bound to the operator, it prevents the RNA polymerase from transcribing the genes. If on the other hand the repressor is not bound to the operator it allows the RNA polymerase to transcribe the genes. If the repressor is naturally bound to the operator it is said to be repressible as it requires external changes to stop binding to the operator. If the repressor is naturally remains unbound, it is said to be inducible as it requires external changes to start binding to the operator.

An example of a repressible operon is the lac operon and an example of an inducible operon is the trp operon, which you can learn more about by clicking the corresponding video on the screen right now!

[michaelkoder]

Great video, but I would like to comment about the end of your video. You mention the lac operon is an example of a repressible operon but in fact it is inducible. Since the lac operon uses lactose as a source of energy, it is only activated or "induced" when glucose levels are low but lactose is present. Otherwise the pathway is always shut off. The trp operon is repressible as prokaryotes need to make tryptophan to survive. The operon is always on as a result, making tryptophan. When tryptophan becomes available, the pathway is "repressed" as continuing the operate the pathway is an inefficient use of resources and waste of energy. Your video says that the trp operon is inducible.

[Rocky-oy]

I learned lot more from this video than 4 days lectures of my college❤

[being.nathan]

Lac operon is inducible and tryptophan operon is repressible.

[vasili-jyyb]

I didn't understand this concept in my cram school cause they were explaining it in a really complex and confusing manner there.

Chat GTP wasn't helping either.

It was only after I saw this video, that I got really clear on this concept.

( I am in 12th btw and I was wondering if they teach this in high school in the US)

[abbystevens]

thank you for making a very complex concept (to me, anyways) incredibly simple and understandable

[LucasLearnz]

Please let me know if you have any questions!