In a line of human cells grown in culture, a geneticist isolates a temperature-sensitive mutation at a locus that encodes an acetyltransferase enzyme; at temperatures above 38°C, the mutant cells produce a nonfunctional form of the enzyme. What would be the most likely effect of this mutation if the cells were grown at 40°C?

A general decrease in transcriptional activation

Explanation:

When acetyl groups are added to histone proteins by acetyltransferase enzymes, the 30-nm chromatin fiber will not be formed because the proteins are prevented from doing so. This further destabilizes the chromatin structure and allows the occurrence of transcription. However, raising the cells to  40°C does not allow the acetyltransferase enzyme to function and hence the acetyl group will be hindered from being added to the histone protein which is the main target of the enzymes. Thus, transcription activation will be blocked because the chromatin and nucleosomes would remain stabilized.

not sure if this is what you'r looking for nnew= nold