Negative supercoiling of DNA favors the transcription of genes because it facilitates unwinding. However, not all promoter sites are stimulated by negative supercoiling. The promoter site for topoisomerase II itself is a noteworthy exception. Negative supercoiling decreases the rate of transcription of this gene. Propose a possible mechanism for this effect and suggest a reason why it may occur.

You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site Say you don’t know which mutant has a defect in the site and which one has a mutation in the binding protein. To figure it out, you construct the two partial diploid strains (i and ii below), and you then assay the levels of the Emu1 and Emu2 proteins in these two strains. F’ (reg1- reg2+ emu1- emu2+) / reg1+ reg2+ emu1+ emu2- F’ (reg1+ reg2- emu1- emu2+) / reg1+ reg2+ emu1+ emu2-   What proteins do you predict will be expressed for strains i and ii if reg2 encodes the regulatory protein and reg1 is the regulatory site?

The following diagram show what is required for an active promoter of a gene of interest, where:A1 = Activator 1A2 = Activator 2Med = MediatorRep = Repressor   Based on the following data, predict: Chromatin conformation Methylation state of the proximal promoter If protein A1 is present or absent If protein A2 is present or absent If the mediator is present or absent If the repressor is absence or present If this gene is likely to be transcribed or notPlease note that this is an "all or nothing" bonus question, and no partial credit will be awarded. Selecting all answers will result in zero points awarded. Selecting at least one incorrect answer will result in zero points being awarded.    Question 28 options:   Euchromatin   Heterochromatin   Methylated promoter   Unmethylated promoter   Activator A1 present   Activator A1 absent   Activator A2 present…

Explain how a transcriptional fusion to a reporter gene, combined with site directed mutagenesis, can indicate key nucleotides in a regulatory region. Name one in vitro technique that can be used to further confirm the significance of these regions.