Question

7. You have identified three fractions, A, B and C that contribute to transcription of your favorite gene. Your initial experiments suggest that each fraction contains either an activator of transcription or a co-activator. You perform a band shift experiment on different combinations of your fractions and obtain the data in the image below.

1 2 3 4 5 6 7 8 О А В С А А В В в ССС A

Which of your fraction(s) most likely contain an activator protein and which most likely contain a coactivator?

A. A most likely contains an activator, and B and C most likely contain a co-activator

B. B most likely contains an activator, and A and C most likely contain a co-activator

C. C most likely contains an activator, and A and B most likely contain a co-activator

D. A and B most likely contain an activator, and C most likely contains a co-activator

E. A and C most likely contain an activator, and B most likely contains a co-activator

F. B and C most likely contain an activator, and A most likely contains a co-activator

Answer 1

E. A and C most likely contain an activator, and B most likely contains a co-activator.

Lane 1 represents the transcript band in the absence of A, B or C. A and C when used alone increases the size and mobility of the transcript unlike B. When A and C are used, a cumulative increase in the size and mobility is observed whereas when B is used in combination with A or C, the shift observed is corresponding to that of A or C only. The addition of fractions A, B and C altogether shows a higher shift compared to that of when A and C are used. This indicates that A and c are capable of bind to the nucleic acid element directly hence they are most likely activators. On the other hand, B can bind only when A and C are bound to the transcript, which indicates that B mostl likely contains a co-activator.