The diagram below represents a hypothetical operon in the bacterium E. coli.  The operon consists of two structural genes (A and B), which code for the enzymes A-ase and B-ase, respectively, and also includes P (promoter) and O (operator) regions as shown.

 When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes A-ase and B-ase are both synthesized at a 50-fold higher rate than in the absence of X.  (X has a molecular weight of about 200.)  Which of the following statements is true of the operon decribed above?

#Question id: 2712

#Unit 2. Cellular Organization

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of cytosine (C) nucleotides in the DNA of promoters of a mammalian system. Which of the following results would she most likely see?

#Question id: 2713

#Unit 2. Cellular Organization

 Which of the following enzymes is not correctly paired with its function?

#Question id: 2714

#Unit 2. Cellular Organization

HAT enzymes react with the side-chain of lysine to form the following structure. What effect will the HAT enzymes have on histones?

#Question id: 2715

#Unit 2. Cellular Organization

The interaction between the positively charged amino terminus of histone __________ and a negatively charged region of the histone fold domain of histone __________ is particularly important for 30 nm fibre formation.

#Question id: 2716

#Unit 2. Cellular Organization

With respect to assembly of every core histone which of the following is wrong?

#Question id: 2717

#Unit 2. Cellular Organization

To reseal the DNA backbone where does topoisomerase gets the energy from?