29) What is the function of DNA toposiomerases?
A) cleaving nucleotides from the ends of DNA
B) adding or removing supercoils
C) methylation of the nitrogenous bases
D) packaging of DNA into nucleosomes
30) _ plays an important
40) The packaging of DNA in cells results in about a _-fold reduction in length compared
to the fully extended DNA (fully stretched out).
41) Which statement is not true about histones?
A) They ar
37) What is unusual about the reaction catalyzed by ribonucleotide reductase?
A) It involves the conversion of -SH groups to -OH groups.
B) It uses a rare derivative of tetrahydrofolate.
C) It has a free radical mechanism.
D) This enzyme and its reaction
28) High levels of _ will almost totally inhibit ATCase.
C) CTP and UTP
D) ADP and UDP
29) Which is the correct order for the synthesis of CTP?
A) UMP UDP UTP CTP
B) GMP GDP GTP CTP
C) UTP TTP CTP
D) UMP CMP CDP CT
18) The pyrimidine ring system is shown below. What is the source of the N-3 during the de novo
biosynthesis of pyrimidines?
19) The pyrimidine ring system is shown below. What is the
5) The purine ring system is shown below. What is the source of the carbon atoms 2 and 8 during
de novo biosynthesis of purines?
A) carbon dioxide
6) The purine ring system
11) Which structure below is PRPP?
12) The first step in the de novo biosynthesis of IMP is a reaction between glutamine and PRPP.
Which statement is not true about this reaction?
A) An amine group is att
10) What would be the product of the transamination of the structure shown below? (The
unionized forms are shown.)
11) Which of the following is/are true concerning transanimation reactions?
A) They can c