The transcription factors are normally bound to the Psf promoter in the presence of both Mg2+ and Ca2+ (c) MetA and MetC . Therefore , (c) MetA and MetC is correct .
Here's the breakdown of the table:
Row 1 (none): This row represents the control group, where no binding sites are present.
As expected, there is no transcription of the Psf gene.
Row 2 (A only): This row shows that when only the A site is present, there is no transcription.
This suggests that MetA alone is not sufficient to activate transcription.
Row 3 (B only): Similar to row 2, the presence of only the B site does not lead to transcription. This indicates that MetB alone is also not sufficient.
Row 4 (C only): Interestingly, the presence of only the C site leads to a low level of transcription.
This suggests that MetC might have some weak activating potential on its own.
Row 5 (A and B only): Again, no transcription occurs when only the A and B sites are present.
This further confirms that neither MetA nor MetB is sufficient alone.
Row 6 (A and C only): This is the first row where we see high levels of transcription.
This indicates that the combination of MetA and MetC is necessary and sufficient for full activation of the Psf gene.
Row 7 (B and C only): Similar to row 6, the presence of both B and C sites results in high levels of transcription.
This suggests that MetB can also cooperate with MetC to activate transcription.
Row 8 (all three): As expected, having all three binding sites present leads to high levels of transcription.
This confirms that MetA, MetB, and MetC all play a role in activating the Psf gene in the presence of both Mg2+ and Ca2+.
Therefore, based on the data in the table, the only option that is consistently associated with high levels of transcription in the presence of both Mg2+ and Ca2+ is the combination of MetA and MetC.
So the answer is (c) MetA and MetC.