Identify which of the following lac operon haploid ge...

Question

Identify which of the following lac operon haploid genotypes transcribe operon genes inducibly and which transcribe genes constitutively. Indicate whether the strain is lac⁺ (able to grow on lactose-only medium) or lac⁻ (cannot grow on lactose medium).
I⁺ P⁺ O⁺ Z⁻ Y⁺

I⁺ P⁺ O⁺ Z⁻ Y⁺

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem. If a strain has the following lac operon genotype lack I minus, lack Z plus, lack Y plus lack A plus. Which of the following statements is therefore true choice. A, the strain will not grow on a lactose. Only medium choice. B the lac operon genes will be transcribed constituently. Choice. C lactose cannot be transported into the cell or D all options are correct. So let's look at our lack Ron genotype and think about what that means for what will happen with the expression of the genes and then the function of the cell. So we look at our four genes and recall that black eye is the gene or the lack of repressor protein while lack Z Y and A are the structural genes. So we see that all of our structural genes are A plus genotype. They are all present and produce their products. Well, it's the lack I gene that is missing. So the lac repressor protein will not be produced. And of course, the lac repressor protein is usually there preventing transcription when lactose is absent. So this means it will not prevent transcription in the absence of lactose as it usually does. So with that in mind, let's look at our answers. Choice A, the strain will not grow on a lactose only medium. Well, we have all the structural genes being expressed just fine. Uh So the strain will be able to use lactose as an energy source as its sole energy source. So choice A is not correct. And so as a result, we can also eliminate choice D all options are correct because we already have one that is not. Then choice B says the lack operon genes will be transcribed constituently. Well, what is constituents, transcription? It is transcription at a relatively constant level regardless of the cell conditions. And this will be true because usually in the presence of the lac repressor, those genes will not be transcribed if lactose is absent but will be in the presence of lactose. It's called the facultative transcription. But in this case, with the repressor not being produced, those genes will just be transcribed at a relatively constant level plus or minus lactose. Finally, choice C lactose cannot be transported into the cell. Well, this is not correct. The enzyme that transports lactose into the cell is permeate. And since permeate is coded for by the gene lac Y, that's just fine. It's fully functional here. And so lactose will be able to be transported. So again, if the strain has this genotype lack I minus lax C plus, lack Y plus, lack A plus. The answer is choice B the lack operon genes will be transcribed constituently as our true statement. See you on the next video.

Identify which of the following lac operon haploid genotypes transcribe operon genes inducibly and which transcribe genes constitutively. Indicate whether the strain is lac⁺ (able to grow on lactose-only medium) or lac⁻ (cannot grow on lactose medium).
I⁺ P⁺ O⁺ Z⁻ Y⁺

Key Concepts

Lac Operon Structure

Inducible vs. Constitutive Expression

Haploid Genotypes and Mutations

Watch next

Identify which of the following lac operon haploid genotypes transcribe operon genes inducibly and which transcribe genes constitutively. Indicate whether the strain is lac⁺ (able to grow on lactose-only medium) or lac⁻ (cannot grow on lactose medium).I⁺ P⁺ O⁺ Z⁻ Y⁺

Key Concepts

Lac Operon Structure

Inducible vs. Constitutive Expression

Haploid Genotypes and Mutations

Watch next

Identify which of the following lac operon haploid genotypes transcribe operon genes inducibly and which transcribe genes constitutively. Indicate whether the strain is lac⁺ (able to grow on lactose-only medium) or lac⁻ (cannot grow on lactose medium).
I⁺ P⁺ O⁺ Z⁻ Y⁺