12–1 DNA
The Components and Structure of DNA
The Components and Structure of DNA
DNA is made up of nucleotides.
A nucleotide is a monomer of nucleic acids made
up of:
• Deoxyribose – 5-carbon Sugar
• Phosphate Group
• Nitrogenous Base
Slide
1 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of DNA
There are four
kinds of bases in
in DNA:
•  adenine
•  guanine
•  cytosine
•  thymine
Slide
2 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of DNA
Chargaff's Rules
Erwin Chargaff discovered that:
•  The percentages of guanine [G] and cytosine
[C] bases are almost equal in any sample of
DNA.
•  The percentages of adenine [A] and thymine
[T] bases are almost equal in any sample of
DNA.
Slide
3 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
•  Because of this, we now know that
Adenine and Thymine pair together and
Cytosine and Guanine pair together
•  A-T
•  C-G
Slide
4 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of DNA
X-Ray Evidence
Rosalind Franklin used X-ray
diffraction to get information
about the structure of DNA.
She aimed an X-ray beam at
concentrated DNA samples
and recorded the scattering
pattern of the X-rays on film.
Slide
5 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of DNA
The Double Helix
Using clues from Franklin’s pattern, James
Watson and Francis Crick built a model that
explained how DNA carried information and
could be copied.
Watson and Crick's model of DNA was a
double helix, in which two strands were
wound around each other.
Slide
6 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of
DNA
DNA Double Helix
Slide
7 of 37
Copyright Pearson Prentice Hall
End Show
12–1 DNA
The Components and Structure of
DNA
Watson and Crick discovered that hydrogen bonds
can form only between certain base pairs—adenine
and thymine, and guanine and cytosine.
This principle is called base pairing.
Slide
8 of 37
Copyright Pearson Prentice Hall
End Show
12–1
Click to Launch:
Continue to:
- or -
Slide
9 of 37
End Show
Copyright Pearson Prentice Hall
12–1
Avery and other scientists discovered that
a.  DNA is found in a protein coat.
b.  DNA stores and transmits genetic
information from one generation to the next.
c.  transformation does not affect bacteria.
d.  proteins transmit genetic information from
one generation to the next.
Slide
10 of 37
End Show
Copyright Pearson Prentice Hall
12–1
The Hershey-Chase experiment was based on
the fact that
a.  DNA has both sulfur and phosphorus in its
structure.
b.  protein has both sulfur and phosphorus in
its structure.
c.  both DNA and protein have no phosphorus
or sulfur in their structure.
d.  DNA has only phosphorus, while protein
has only sulfur in its structure.
Slide
11 of 37
End Show
Copyright Pearson Prentice Hall
12–1
DNA is a long molecule made of monomers
called
a.  nucleotides.
b.  purines.
c.  pyrimidines.
d.  sugars.
Slide
12 of 37
End Show
Copyright Pearson Prentice Hall
12–1
Chargaff's rules state that the number of guanine
nucleotides must equal the number of
a.  cytosine nucleotides.
b.  adenine nucleotides.
c.  thymine nucleotides.
d.  thymine plus adenine nucleotides.
Slide
13 of 37
End Show
Copyright Pearson Prentice Hall
12–1
In DNA, the following base pairs occur:
a.  A with C, and G with T.
b.  A with T, and C with G.
c.  A with G, and C with T.
d.  A with T, and C with T.
Slide
14 of 37
End Show
Copyright Pearson Prentice Hall
END OF SECTION