Chapter 13 DNA Technology
The New Genetics-Genetic
Engineering
DNA Identification
No 2 people (other than identical twins) have
the same DNA yet everybody's DNA only
differs by 0.10 %.
But that 0.10 % difference is enough to
identify individuals. Scientists use DNA
identification for:
- identifying human remains
- establishing paternity (who's your daddy?)
- evidence in criminal cases
Manipulating Genes
In order to do DNA identification, you have to be
able to manipulate genes.
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Restriction Enzymes – Bacterial enzymes
capable of cutting DNA into smaller fragments.
-Recognize certain base pair sequences and
cut the DNA at specific sites
-EcoR1— recognizes GAATTC and cuts
between G and A
-Sticky ends – “z shaped” ends of the cut DNA
DNA Technology Techniques
DNA Fingerprinting – Analyzing differences
in an individual’s DNA.
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RFLP – Restriction Fragment Length
Polymorphism
-Breaks DNA sample into several pieces using
a restriction enzyme
-Gel electrophoresis – separates DNA
fragments based on length
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Gel Electrophoresis
1.) DNA fragments are placed in a slightly porous
agarose gel.
2.) An electric charge is applied to the gel.
-DNA travels toward the positive end.
-The smaller the piece of DNA, the faster it will travel.
3.) After a set time, the gel is stained and bands are
formed from the DNA fragments.
-These bands give a distinct “fingerprint” of an
individual
PCR—Polymerase Chain Reaction
Before crime labs can test DNA, they usually need
to make copies! (Most criminals only leave small
samples)
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Used to make tons of DNA from tiny amounts
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Very necessary in crime labs
The steps…
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DNA unzipped by DNA polymerase
Primers attach to the unzipped DNA
DNA polymerase attaches the correct nucleotides to the
DNA strands
We now have two copies of the original DNA
Repeat the above steps to make 4…6…8 …16…etc.
Transplanting Genes
(Recombinant DNA)
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DNA technology is sometimes used to modify
the genome of an organism or cell
This is called genetic engineering
Recombinant DNA is the result of combining
the genes of 2 different kinds of organisms
Why do this?
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Lots of reasons, some things scientists have done:
made insulin for diabetics, made vegetables that
last longer
These zebra fish have been genetically modified to
glow in the dark using a gene from a jellyfish.
Originally they were designed to glow in polluted
water but now they are being sold as pets. Right
or wrong? What do you think?
How can scientists modify an
organism's genes?
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Cloning vectors – a
carrier used to clone a
gene and transfer it
from one organism to
another
-Plasmid – small
pieces of extra DNA in
bacteria often used as
cloning vectors
For example, making insulin for diabetics
to control blood sugar
1.) The insulin gene is removed from Human DNA
using a restriction enzyme.
2.) A plasmid is removed from a bacteria and cut
using the same restriction enzyme.
3.) The insulin gene is then placed into the plasmid
and the plasmid is then inserted into the bacteria.
The new plasmid is called recombinant DNA since it
comes from two original sources.
4.) The bacteria reproduces and each new bacteria
produces insulin.
Insulin the old way.....
They had to
slaughter pigs &
cows and get the
insulin from their
pancreas
Insulin the new way....
Transplanting Genes (cont’d)
Recombinant DNA – DNA made from more than
one source.
-i.e. The plasmid with the human insulin
gene inserted.
Transgenic Organism – an organism receiving
recombinant DNA.
-i.e. The bacteria receiving the insulin
gene.
Transplanting Genes (cont’d)
Problems with this approach
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Many genes require “on/off” switches
-Can be remedied by inserting the “on/off”
switch gene.
-Or by inserting the gene in a region of the
plasmid which contains a gene that
is
frequently turned on.
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