Homework (chapter 1 of Biology - Units 3 & 4)

[NN900]

Hello,...
Can someone please help me with this question:
"A mutation in one gene (G1) affects just one kind of protein produced by a cell. A mutation in another gene (G2) affects a large number of different kinds of proteins produced by that cell. One of these genes carries the coded instructions to make one kind of tRNA. The other carries coded information to make one kind of salivary enzyme.
Which is more likely to be the gene for the tRNA: G1 or G2? Explain."

I'm thinking that it would be G2. (G2 is more likely to be the gene for the tRNA because if it affects a large number of different kinds of proteins produced by that cell, thus it will be more likely to carry the coded instruction to make tRNA than G1.)

Can someone please let me know if my "assumption" is right and elaborate more on the correct answer of this question if possible?

Cheers.

[caffinatedloz]

Hi NN900,
I agree with your assumption. As tRNA helps build many proteins, a mutation that disrupts the functioning of tRNA would affect a large number of proteins produced by the cell. As salivary enzymes are not involved in building other proteins, a mutation disrupting the production of a salivary enzyme would only affect one protein produced.

[NN900]

Hello, caffinatedloz
Thank you so much for letting me know 

[NN900]

Hello, there
Can someone please explain questions 14 (d) and (e) to me? (I'm a bit confused with these two questions).
But I answered question 14 (d) [not sure if my answer is right or not]

=> 14(d)___If the tryptophan is not available from the environment, then the structural genes in the trp operon would be activated or expressed. Therefore, <=> absence of tryptophan = trp operon:ON
It would be great if someone can help me with this. 

Cheers.

[Domek]

Hello, there
Can someone please explain questions 14 (d) and (e) to me? (I'm a bit confused with these two questions).
But I answered question 14 (d) [not sure if my answer is right or not]

=> 14(d)___If the tryptophan is not available from the environment, then the structural genes in the trp operon would be activated or expressed. Therefore, <=> absence of tryptophan = trp operon:ON
It would be great if someone can help me with this. 

Cheers.

Hi NN900,
The question layout here is a bit confusing. I think 'under these conditions' is actually referring to the conditions above. So, for question d) they would be 'Consider a situation in which tryptophan is present in the environment...' In this case, because the trp operon encodes enzymes that are involved in the synthesis of tryptophan, it would be a waste of resources for the E. coli to produce tryptophan. Therefore, the tryptophan binds to a protein called trp repressor, activating and allowing it to bind to the trp operator, a region adjacent to the promoter. This prevents RNA polymerase from binding to the promoter and initiating transcription. Therefore the trp operon is repressed.

But yes, if you were using the 'under these conditions' below the question as you've highlighted, your answer would be correct.

For question e), I believe 'under these conditions' is referring to 'If tryptophan is not available from the environment...'. So, in order for the bacteria to manufacture tryptophan themselves, they will need to activate the trp operon.

It looks like this question doesn't assume prior knowledge of how the trp operon functions so probably doesn't require as much detail as I've included. However, I've put it in anyway as the trp operon is included in the new 2022 study design.

I hope that helps.

[NN900]

Hi NN900,
The question layout here is a bit confusing. I think 'under these conditions' is actually referring to the conditions above. So, for question d) they would be 'Consider a situation in which tryptophan is present in the environment...' In this case, because the trp operon encodes enzymes that are involved in the synthesis of tryptophan, it would be a waste of resources for the E. coli to produce tryptophan. Therefore, the tryptophan binds to a protein called trp repressor, activating and allowing it to bind to the trp operator, a region adjacent to the promoter. This prevents RNA polymerase from binding to the promoter and initiating transcription. Therefore the trp operon is repressed.

But yes, if you were using the 'under these conditions' below the question as you've highlighted, your answer would be correct.

For question e), I believe 'under these conditions' is referring to 'If tryptophan is not available from the environment...'. So, in order for the bacteria to manufacture tryptophan themselves, they will need to activate the trp operon.

It looks like this question doesn't assume prior knowledge of how the trp operon functions so probably doesn't require as much detail as I've included. However, I've put it in anyway as the trp operon is included in the new 2022 study design.

I hope that helps.

Thank you so much for your help  Your explanation helps a lot and it makes more sense about the trp operon function.
Have a nice day!