RNA interference can repress proteins by all of the following mechanisms EXCEPT:
a. promoting histone acetylation.
b. promoting histone methylation.
c. promoting mRNA degradation.
d. blocking translation.
The following are all examples of a histone modification EXCEPT:
a. acetylation to repress transcription.
b. acetylation to activate transcription.
c. methylation to repress transcription.
d. methylation to activate transcription.
D, B
A,C
RNA interference can repress proteins by all of the following mechanisms EXCEPT:
a. promoting histone acetylation.
The following are all examples of a histone modification EXCEPT:
a. acetylation to repress transcription.
I know for a fact that both of these are correct.
To determine the correct answers, let's analyze each option and eliminate the ones that are incorrect.
For the first question about RNA interference mechanisms, we want to find the mechanism that does NOT repress proteins. RNA interference typically represses proteins by targeting mRNA, either by degrading it or blocking its translation. So, let's evaluate each option:
a. promoting histone acetylation: Histone acetylation typically promotes gene expression, so it is not a mechanism of repression. This option is a potential correct answer.
b. promoting histone methylation: Histone methylation can have both activating and repressive effects on gene expression, depending on the specific amino acids that are methylated and the degree of methylation. It is plausible that promoting histone methylation could lead to repression, so we cannot eliminate this option yet.
c. promoting mRNA degradation: mRNA degradation is indeed a mechanism by which RNA interference represses proteins. This option is a potential correct answer.
d. blocking translation: Blocking translation is another mechanism by which RNA interference can repress proteins. This option is a potential correct answer.
Now let's move on to the second question about histone modifications:
a. acetylation to repress transcription: Histone acetylation is generally associated with transcriptional activation, not repression. This option is a potential correct answer.
b. acetylation to activate transcription: Histone acetylation is indeed associated with transcriptional activation. This option is not a correct answer.
c. methylation to repress transcription: Histone methylation can have repressive effects on gene expression, so this option is not a correct answer.
d. methylation to activate transcription: Histone methylation can also have activating effects on gene expression, so this option is not a correct answer.
Based on our analysis, the correct answers are:
First question: a. promoting histone acetylation (because histone acetylation promotes gene expression, not repression).
Second question: b. acetylation to activate transcription (because histone acetylation activates gene expression, not repression).
In summary, the correct answers are:
For the first question: a. promoting histone acetylation.
For the second question: b. acetylation to activate transcription.