Question

Polycomb and Trithorax complexes With DNase I Without DNase I Days of induction 0 0 1 24 Probe X Probe Y Southern blot Southern blot Northern blot 1. The PcG complex is associated with gene repression while the TrxG complex is important for gene activation. At day zero of muscle cell differentiation, which complex is most active at a. Gene X? b. Gene Y? What histone modification is most likely present at the gene X promoter on day 4, H3K4me3 or H3K27me 2. 3? Is your answer a mark of repressed or active chromatin? 3. GSK126 inhibits the catalytic activity of EZH2 in cell lines. After day 1 of muscle cell differentiation, you treat the cells with GSK126 (arrow) and grow them until day 4. Comparing to the original results above, fill in the expected Southern and Northern blot results for days 2 and 4 for genes X and Y With DNase Without DNase I Days of induction 0 1 2 4 0 1 2 4 Probe X Southern biot Southern blot Northern blot Days of induction 0 1Ψ2 1 24 Probe Y Southern blot Southern blot Northern blot

Answer 1

1) Northern blot detects RNA. If the gene is active, then RNA will b synthesized. Since, in the northern blot, RNA for gene Y is observed at day 0 of differentiation, the right option is b or gene Y.

2) On day 4, it is HeK4me3 modification on gene X promoter as there is active transcription of this gene (Shown by northern blot). HeK4me3 is a histone modification that is involved in activation of transcription. It is a mark of active chromatin.