Ch. 16 DNA: The Genetic Material Intro In 1953, James Watson and Francis Crick presented their model of DNA to the world. Nucleic Acids (DNA: Deoxyribonucleic acid, RNA: Ribonucleic acid) have a unique ability to replicate itself. DNA’s ability to replicate itself precisely is
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DNA: The Genetic Material
important for its transmission from one
generation to the next.
to discover this transforming material.
-The number of Adenine = Thymine
-The number of Cytosine = Guanine
-Maurice Wilkins and Rosalind Franklin
strands, each strand with the sugar-
phosphate chains on the outside and the
nitrogenous bases on the inside.
-Only a pyrimidine-purine pairing would produce the 2-nm diameter indicated by the X-ray data.
between one another:
-A = T (two)
-G = C (three)
** This confirms
A portion of gene has the following
sequence of nucleotides:
-Watson and Crick presented
their DNA model in 1953.
-They, along with Maurice
Wilkins won the Noble Prize in
Medicine in 1962.
-This means that when two strands
of DNA are made, each one will have
a new strand and an old one. The old
strands will act as “templates” to the
new complimentary strand.
1. In their experiments, they labeled the
nucleotides of the old strands with a
heavy isotope of nitrogen (15N) while any
new nucleotides would be indicated by a
lighter isotope (14N).
one error per billion nucleotides.
the DNA strand where replication takes
-The nucleotides that are attached to the
newly formed strands are called
Each has a nitrogen base, deoxyribose,
and a triphosphate tail.
two phosphate groups are hydrolyzed
to form pyrophosphate.
pyrophosphate to two inorganic
phosphate molecules drives the
polymerization of the nucleotide to
the new strand.
-DNA can only replicate in the 5’ 3’
replicates from 5’ 3’.
replicates from 5’ 3’,
but by forming
-The Okazaki fragments
are then joined by
Creates a primer.
Adds nucleotides to
the 3’ end; replaces
Joins the Okazaki
Also, under normal cellular
conditions, DNA can undergo spontaneous
Xeroderma Pigmentosum causes an
individual to be very sensitive to sunlight.
UV light can cause two adjacent Thymine
nucleotides to form a dimer. The dimer
buckles the DNA strand and interferes with
Causes skin cancer.
a short RNA fragment
that serves as a
template for a new