How do you read the graph You test the effect on mRNA X of e

How do you read the graph?

You test the effect on mRNA X of expressing protein Y and observe the following. What function of protein Y is supported by the data? A: Activates mRNA X degradation B: Stabilizes mRNA X C: Represses mRNA X translation D: Activates mRNA X translation E: Activates mRNA X transcription

Solution

Dear Student,

Here, mainly the idea is to understand the impact of protein on mRNA. The sucrose gradient indicates the mRNA concentration here since sucrose is used to measure the mRNA (instead of nycodenz gradient).

Thus, we have to look at how activity of protein Y- leads to concentration of mRNA (by sucrose gradient),

The negative activity of protein Y is leading to light sucrose gradient, meaning the mRNA is getting destroyed/repressed when the protein Y is not acting.

On the other hand, when +Protein Y is acting, the mRNA is on the heavy side- hence there is an indication that more mRNA is produced here. However, the last blot of the heavy side is not as thick, indicating quantity may be reduced.

Thus we can read by combining the mRNA quantity proportion (by sucrose) and activity of Protein Y, and conclude that by the activity of protein Y, the mRNA is stabilized. (B)

I would be assuming here that it stabilizes since there is no increase in the concentration of mRNA with duration of activity of the protein with time, rather, it stays neutral. If you could select two options, it would be B and E, since there is no data indicating protein Y does NOT increase the transcription of mRNA. It would be contextual in that case.

The options including translation will be eliminated automatically since the Northern blot is used to measure the mRNA and not the proteins produced from mRNA (translation= protein from mRNA, transcription= mRNA from DNA)

All the best!