CH. 11: DNA ANALYSIS
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DNA: Deoxyribonucleic Acid
 Nucleotide:
 Sugar (deoxyribose)
 Phosphate
 Nitrogenous Base
 4 different bases:
 Adenine
 Thymine
 Cytosine
 Guanine
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DNA: Deoxyribonucleic Acid
 Found in all nucleated body cells:
 WBC, saliva, semen, urine, hair root, teeth,
bone, soft tissue, etc.
 RBC have no nuclei, therefore DNA in blood
samples comes from WBC
 Most abundant in buccal (cheek) cells
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Restriction Enzymes
 Bacterial defense mechanism
 Cut DNA molecules at specific sites
(certain nucleotide sequences)
We will be
using Hae III
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Hae III cut site
...C C G G...
...G G C C...
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Gel Electrophoresis
 Uses electric
current to separate
DNA fragments by
size
 Smaller DNA
pieces migrate
faster through gel
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DNA Fingerprinting
 Everyone’s DNA
sequence is slightly
different (0.1%, or 3
million base pairs)
 Restriction enzymes
cut different sized
pieces (fragments)
 RFLP = restriction
fragment length
polymorphism
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Uses of DNA Profiling
 To identify potential
suspects
 To exonerate
individuals
 To identify crime and
casualty victims
 To establish
paternity
 To match organ
donors
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DNA Exoneration
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DNA evidence makes up
part of the case against the
defendant
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Polymerase Chain Reaction (PCR)
 Uses DNA
polymerase to
amplify DNA (make
a LOT of copies of a
target sequence)
 Valuable when
amount of evidence
is minimal
 Millions of copies
can be made from a
single speck of
blood
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Short Tandem Repeats (STR)
STR’s are locations (loci) on the chromosome
that contain short sequences of 2 to 5 bases
that repeat themselves in the DNA molecule.
The advantages of this method are that it:
 Offers greater specificity*
 Requires less time
 Requires smaller sample size
 Is less susceptible to DNA degradation
*The number of possible individual STR profiles greatly exceeds the
estimated number of humans who have ever lived, so it is nearly
impossible for a random match to occur.
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FBI’s CODIS DNA Database
Combined DNA Index System
 Used for linking serial crimes and
unsolved cases with repeat offenders
 Launched October 1998
 Links all 50 states
 Requires 4+ RFLP markers and/or
13 core STR markers
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CODIS = Combined DNA
Index System
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STR Genetic Profile Allelic Ladders
VWA
D3S1358
AMEL
D8S1179
D5S818
FGA
D21S11
D13S317
D18S51
D7S820
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STR Example Profile
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STR Interactive Animation
The website below has an informative STR
animation demonstration.
Click on “human identification”, “profiling” and
then on the third circle called “Today’s DNA
Profiling” to see the demonstration.
http://www.dnai.org/d/index.html
Print & complete the STR WORKSHEET
before your next NB check!
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Mitochondrial DNA (mtDNA)




Found in cytoplasm of cells
Inherited only from the mother (egg cell)
mtDNA is constructed in a circular or loop
As opposed to nuclear DNA, analysis of
mtDNA is more:
 rigorous
 time consuming
 Costly
 Is used when nuclear DNA typing is not
possible (i.e. skeletal remains)
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