THE STRUCTURE OF DNA
DNA
Deoxyribonucleic acid
Large molecule called a
polymer
 Polymer means molecule with many units
Units or monomers of DNA
are nucleotides
NUCLEOTIDES
Made of 5-carbon sugar
called deoxyribose
Deoxyribose contain a
phosphate group and one
of four nitrogen bases
4 nitrogen bases




A for adenine
G for guanine
C for cytosine
T for thymine
PURINE BASES
Adenine
Adenine and guanine
The larger of the 2 types of
bases
Have a double ring structure
Guanine
PYRIMIDINE BASES
Cytosine
Cytosine and Thymine
Have a single ring structure
Thymine
DEOXYRIBOSE SUGAR
3 oxygen and 5 carbon atoms
which make up the DNA
“backbone”
The hydroxyl groups’ carbons
link to phosphates to form
this “backbone”
dAMP: Deoxyadenosine monophosphate, a
nucleotide containing adenine, a 2'-deoxyribose sugar
and phosphate, part of DNA structure.
dCMP: Deoxycytosine monophosphate,
a nucleotide containing cytidine, a 2'deoxy sugar, and phosphate, part of
DNA structure.
DOUBLE HELIX
DNA is composed of twisting
strands of nucleotides
Each strand is a helix or
spiral staircase
2 strands are bound together
to create a double helix
Double helix
CONFIGURATION OF DNA
A & T always join together
and form 2 hydrogen
bonds
C & G always join together
and form 3 hydrogen
bonds
Think A & T and UNCG to
remember these.
DNA FINGERPRINTING
DEFINITION
Method of identification that
compares fragments of
DNA
DNA is the genetic material
found in the cell nucleus
DNA of each individual is
unique, with identical twins
being the only exception
CONSTRUCTING A FINGERPRINT
A “fingerprint” is constructed
by
 Obtaining a DNA sample from body tissue
or fluid
 Cutting this sample into pieces using
enzymes
 Arranging these pieces using gel
electrophoresis
GEL ELECTROPHORESIS Refers to the forced movement of
molecules by electricity
Separates macromolecules (large
molecules) on the basis of
size, electric charge, and other
physical properties.
The gel is like Jell-o.
Electrophoresis describes the
moving of the charged DNA
 Electro: energy of electricity
 Phoros: to carry across
STEPS IN GEL ELECTROPHORESIS
Holes created in gel to hold DNA
solution
DNA solutions loaded into holes
Gel is “excited” by electricity and
small molecules move through
the gel
Photograph is taken to save the
results of the fingerprint
2 matching fingerprints indicate
they are probably from identical
sources
USES OF FINGERPRINTING
Discovery of genetic causes
of diseases
Mapping the human genome
(2003)
Forensic science
Paternity testing
http://www.sumanasinc.com/webcontent/an
imations/content/gelelectrophoresis.html
REFERENCES
Adenine and guanine http://www.chemsoc.org/networks/learnnet/cfb/nucl
eicacids.htm
Thymine and cytosine http://www.chemsoc.org/networks/learnnet/cfb/nucl
eicacids.htm
dAMP & dCMP http://www.cancerwatch.org/glossary/glossary_7.cfm
REFERENCES
Double helix http://alum.mit.edu/ne/opendoor/200507/images/d
ouble-helix.jpg
A&T logo – www.ncat.edu
UNCG logo – www.uncg.edu