09-27-2006, 04:27 PM
. The answer is b. (Murray, pp 412“434. Scriver, pp 3“45. Sack, pp 3“29.
Wilson, pp 99“121.) A nucleoside consists of a purine or pyrimidine base
linked to a pentose sugar. The 1′carbon of the pentose is linked to the nitrogen
of the base. In DNA, 2′-deoxyribose sugars are used; in RNA, ribosesugars are used. Nucleotides are phosphate esters of nucleosides with one to
three phosphate groups, such as adenosine monophosphate (AMP), adenosine
diphosphate (ADP), or adenosine triphosphate (ATP). The nitrogenous
bases are adenine, thymine, guanine, and cytosine in DNA, with thymine
replaced by uridine in RNA. Nucleotide polymers are chains of nucleotides
with single phosphate groups, joined by bonds between the 3′-hydroxyl of
the preceding pentose and the 5′-phosphate of the next pentose. Polymerization
requires high-energy nucleotide triphosphate precursors that liberate
pyrophosphate (broken down to phosphate) during joining. The
polymerization reaction is given specificity by complementary RNA or DNA
templates and rapidity by enzyme catalysts called polymerases
Wilson, pp 99“121.) A nucleoside consists of a purine or pyrimidine base
linked to a pentose sugar. The 1′carbon of the pentose is linked to the nitrogen
of the base. In DNA, 2′-deoxyribose sugars are used; in RNA, ribosesugars are used. Nucleotides are phosphate esters of nucleosides with one to
three phosphate groups, such as adenosine monophosphate (AMP), adenosine
diphosphate (ADP), or adenosine triphosphate (ATP). The nitrogenous
bases are adenine, thymine, guanine, and cytosine in DNA, with thymine
replaced by uridine in RNA. Nucleotide polymers are chains of nucleotides
with single phosphate groups, joined by bonds between the 3′-hydroxyl of
the preceding pentose and the 5′-phosphate of the next pentose. Polymerization
requires high-energy nucleotide triphosphate precursors that liberate
pyrophosphate (broken down to phosphate) during joining. The
polymerization reaction is given specificity by complementary RNA or DNA
templates and rapidity by enzyme catalysts called polymerases