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Chapter 13
Section 1 DNA Technology
DNA Identification
 Only .10% of the human genome varies from person to
person
 98% of our genetic makeup does not code for any
protein.
 Called noncoding DNA
Steps in DNA Identification
 4 main steps
 Isolate the DNA in a sample and, if needed, make copies
 Cut the DNA into shorter fragments that contain repeating
sequences
 Sort the DNA by size
 Compare the size fragments in the unknown sample of
DNA to those of known samples of DNA
 If a match occurs, a person’s identity is known
Copying DNA:PCR
 Often the DNA samples collected are too small
 Polymerase Chain Reaction (PCR) is a technique that quickly
produces many copies of a DNA fragment
 Use primers, artificially made pieces of single stranded DNA
polymerase to initiate replication
Cutting DNA
Restricting Enzymes
 Restriction enzymes-bacterial
proteins used to cut long DNA
molecules into shorter pieces
 These enzymes are called
endonuclease
 Will recognize specific short DNA
sequences and cut the DNA at,
or near the targeted sequence.
 Sometimes will leave “sticky
ends” to aid complementary
sequences in binding.
Sorting DNA by size
Gel Electrophoresis
 Gel electrophoresis separates nucleic acids or proteins
according to their size and charge
The resulting pattern of
bands is called a DNA
fingerprint
Comparing DNA:
DNA Fingerprints
A technician will permanently
preserve DNA by placing a positively
charged nylon membrane over the
gel
The DNA molecules in the gel are
negatively charged, and therefore
stick to the membrane
Scientists will compare this
membrane to the membrane of the
targeted DNA of interest.
Is this accurate?
 DNA fingerprinting typically compares 5-13 repeating
strands of nucleotides.
 Crime labs compare 13 strands
 13 strands will produce the odds that 2 people will
share the DNA profile at around 1 in 100 billion.
 There are roughly 7 billion people in the world
 I would say pretty good odds!
Recombinant DNA
 The previous techniques are used to modify the
genome of a living cell or organism.
 Genetic engineering-the process of altering the genetic
material of cells or organisms to allow them to make a
new substance
 Recombinant DNA results when DNA from two different
organisms are joined
Plasmids
 Plasmids are small rings of DNA found
naturally in some bacterial cells in
addition to the main bacterial
chromosomes.
Steps of transferring insulin
genes
Bacterial and targeted DNA
DNA is cut with restriction
Enzymes
DNA segments are joined at
sticky ends, using DNA ligase
Recombinant DNA is then
inserted into host bacterium
After bacterium have been
allowed to grown into
colonies, a probe will be used
to identify targeted DNA
Probe
 A probe is a strand of RNA or single-stranded DNA that is labeled
with a radioactive element or florescent dye
 To determine which of the colonies contain the desired strand of
DNA, researches will view them under ultraviolet lights or exposed
to photographic film.
Medical Uses
 In 1982, recombinant DNA was made by inserting human gene for
insulin into a bacterial plasmid
 Since 1982 more than 30 products have been made using DNA
technology
 Types of uses
 Clotting factors
 Human growth hormone for people with growth defects
 Factors to treat immune-system deficiencies and anemia
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