The transcription of -galactosidase and permease is inducible ...

Question

The transcription of -galactosidase and permease is inducible in lac⁺ bacteria with a wild-type lac operon. Explain the mechanism by which lactose gains access to the cell to induce transcription of the genes.

Accepted Answer

Hi, everybody. Here's our next question. It says which of the following statements regarding the enzyme, beta galactosidase is true. And our answer choices are B it breaks the beta galacto cytose linkage to release glucose and galactose. Choice B. It converts lactose to allo lactose. Choice C. It also cleaves alo lactose which is not used for induction or d all of the above. So let's recall what beta galactic ciss does and then choose among our answers. Remembering that we do have that all of the above option. So beta galacto CYA is involved in the metabolism of lactose. We can recall that lactose is a disaccharide made up of one molecule glucose and one of galactose and beta galacto CYA or beta Gau as I'll shorten it cleaves the bond between the two sugars so that freeze glucose and galactose as mentioned in choice A, it breaks the beta galactica linkage to release glucose and galactose. So choice A is definitely correct, but I'm just going to put a dot Next to it since I do have the option of having more than one correct answer. So that is sort of the primary um thing that beta galactic is does uh helping to break down lactose but it can do something else as well as cleaving the bond between the two sugars. Um beta gal has in a smaller, smaller function, converts lactose to its isomer allo lactose. So a small amount of the lactose is then converted by beta galactose to allo lactose. Alo lactose then goes on to bind two the lac repressor protein. And that causes the induction of transcription of the lac operon genes necessary to digest lactose. Because by binding the black repressor, the repressor is released from its binding site allowing R N A polymer to come in and transcribe those genes. So as we have in choice B, it converts lactose to alo lactose. That is also correct. We've now got more than one correct answer. So if I were on a test and moving quickly, I would select choice D all of the above because I know I already have more than one. That's correct. But in the interest of being through, we will look at choice C also, it says it also cleaves alo lactose, which is not used for induction. And this is also true. So any alo lactose that is not needed to bind to the repressor protein is cleaved in the same way with that bond between glucose and galactose and releases the two sugars. So choice C also correct, meaning that certainly in terms of which of the following statements regarding the enzyme beta Galacto CTAs is true choice. D all of the above is our answer. See you in the next video.

The transcription of -galactosidase and permease is inducible in lac⁺ bacteria with a wild-type lac operon. Explain the mechanism by which lactose gains access to the cell to induce transcription of the genes.

Key Concepts

Lac Operon

Induction Mechanism

Permease Function

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