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Ch 7 DNA Fingerprinting
Without peeking, can you write out what DNA
stands for?
Deoxyribonucleic Acid
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Cool Things About DNA
The Human Genome consists of the total amount of
DNA in a ? , contained in the chromosomes and
mitochondria. The genome consists of ? base
pairs of DNA.
cell
3,000,000,000
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Cool Things About DNA
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Cells can contain ? feet of DNA. In an
average meal, you eat approximately 55,000,000
cells equaling 63,000 - 93,000 miles of DNA.
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Cool Things About DNA
April 14, 2003 the human genome was completed.
Many scientists hailed the completion as the
greatest human achievement since reaching the
moon? At a rate of 100 letters per minute, it
would take you ? years, without breaks, to
read aloud the entire sequence.
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Introduction to Biological Evidence in Forensics

• DNA fingerprinting, also known as DNA profiling,
  is used in criminal legal cases with a high
  degree of accuracy.
• Biological evidence such as blood, saliva, urine,
  semen, and hair is examined for the presence of
  inherited traits in DNA.

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The Function and Structure of DNA

• DNA molecules make up chromosome structures and
  are found in the nucleus of most cells in the
  human body.
• Organize from smallest to largestcell, DNA,
  nucleus, chromosome, gene.

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Karyotype picture of chromosomes
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Male with Downs Syndrome (Trisomy 21)
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Cool Things About DNA
2-3 of the total DNA carries instruction to
make protein. The rest is referred to as junk
DNA. Remember we all save junk.. Maybe
this too is genetic?
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Only ? of the total DNA (genome) carries
instructions to make protein. The rest is
referred to as ? DNA. Remember we all save
junk.. This too may be genetic?
2-3 of the total DNA carries instruction to
make protein. The rest is referred to as junk
DNA. Remember we all save junk.. Maybe
this too is genetic?
junk
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DNA Identification

• Junk DNA contains many of the unique patterns of
  repeated base sequences that identify
  individuals.
• In a human population, these are called
  Polymorphisms.
• Junk DNA (introns) does not code for proteins
  98.5 of genome

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DNA Identification

• Variable Number of Tandem Repeats (VNTR)
• The number of copies of the same repeated base
  sequence in junk DNA varies among individuals.
  Some can be 9-80 bases in length, therefore are
  more difficult to separate on gel.
• Short Tandem Repeats (STR)
• These usually are only 2-5 bases in length and
  are becoming the preferred sequences for
  analysis.

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• VNTR and STR data are analyzed for (a) tissue
  matching and (b) inheritance matching.
• Population genetics is the study of variation in
  genes among groups of individuals.
• Calculations can be made based on these groups to
  determine the probability a random person would
  have the same alternative form of a gene (an
  allele) as (a) a suspect in a crime or (b) an
  alleged father in a paternity case.

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Preparing DNA Samples for Fingerprinting--Extract
ion

• Cells are isolated from biological evidence such
  as blood, saliva, urine, semen, and hair.
• The cells then are disrupted to release the DNA
  from proteins and other cell components.
• Once released, the DNA can be extracted from the
  cell nucleus.

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DNA Fingerprint from Gel Electrophoresis

• DNA is mixed with restriction enzymes (REs).
• The REs cut apart the DNA in specific places
  forming different sized fragments.
• The DNA is loaded into the wells on an agarose
  gel.
• An electric current is passed through the gel
  separating the fragments by size.

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Cool Things About DNA
99.9
Human DNA is ? identical to each other
99.1 to chimps 90 to mice 85 to Zebra
fish 50 to bananas 21 to worms 7 to bacteria
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Sources of DNA

• A perpetrator may leave biological evidence, such
  as saliva or blood, at a crime scene.
• This individual evidence is capable of
  identifying a specific person.
• But a small amount of biological evidence might
  be considered only trace evidence, and it may be
  consumed during forensic testing.

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Amplification of DNA Trace Evidence

• In 1993, the Polymerase Chain Reaction (PCR)
  technique was invented. It generates multiple
  copies of DNA evidence.
• Why is this technique helpful?

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Cool Things About DNA
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• Humans have ? chromosomes
• Dove 16
• Gorilla ?
• Banana 66
• Dog 78
• Butterflies ?

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380
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Cool Things About DNA
It took researchers 9 years in the 1980s to
discover the gene for cystic fibrosis, 9 days in
1999 to discover the gene for Parkinsons
disease, and ? seconds in 2001 to discover the
gene for Crohns disease. Amazing Science!
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DNA Probes

• The DNA synthetic probe binds to complimentary
  bases in the strand.
• In most criminal cases, 6-8 probes are used.
• Which gel below was probed? How do you know?

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Cool Things About DNA
In forensics, a DNA profile (often called DNA
fingerprinting) looks at ? specific DNA
markers. That equals a 1 in 10 trillion chance of
another identical profile. The FBI DNA database
is called ? (COmbined DNA Index System)
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CODIS
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Analysis of DNA Fingerprints in Paternity Cases

• http//school.cengage.com/forensicscience/