An enzyme that will catalyze the separation of the strands of the
DNA double helix during replication.
A nitrogenous base (purines such as adenine or guanine;
pyrimidines such as uracil, thymine, or cytosine) in an A-P-glycosidic
linkage to a pentose sugar (deoxyribose in DNA and ribose in RNA).
A nucleoside that has a phosphoester bond to one of the
hydroxyl groups of the pentose sugar.
An enzyme that will add nucleotides to a growing nucleic
acid chain using a template strand to determine which nucleotide is
added. A nucleoside triphosphate condenses with the growing strand
1-P-D-ribofuranosyl-1A-1,2,4-triazole-3-carboxamide; a purine
nucleoside analog that exhibits antiviral activity against a broad spec-
trum of DNA and RNA viruses.
D ISC U SSIO N
DNA and RNA are both polymers of nucleosides joined by 3
consists of a
base in a glycosidic link with a pentose sugar.
of both DNA
and RNA is formed by the
phosphate bridges between the 3
group of one pentose and the 5
-hydroxyl group of another.
nous bases form the “side chains.”
DNA contains the bases adenine (A),
guanine (G), cytosine (C),
RNA contains A,
G, and C but has uracil (U) instead of T.
pentose sugar in DNA is
RNA it is ribose.
most stable DNA structure
is formed when
chains are joined by hydrogen bonding between the side chain bases.
base pairing is specific in that
adenine forms hydrogen bonds with thymine,
guanine forms hydrogen bonds with cytosine.
The result is an
antiparallel double helix in which one polynucleotide strand runs in the
while the other runs in the 3
' direction. The
groups are located on the outside of the double helix
forming the “stair steps” in the center of the spiral. RNA,
on the other hand,
(the exception is certain RNA viruses), but the
strand can loop back on itself and form regions of base pairing
(A with U
and G with C). The presence of the
hydroxyl group at the 2
RNA much more susceptible to hydrolysis and decreases its stability.
double helical structure of DNA must be disrupted
during almost all
in which it participates, including
DNA replication and
repair, as well as transcription
of the DNA sequence information to RNA.
double helix can be separated, or denatured, by
increasing the temperature
to well above 50°C (122°F). If the temperature is
carefully decreased, renaturation occurs when the base pairs reform. Under
these conditions, hybridization can be induced by allowing the single strands