INTRODUCTION TO GENETIC ENGINEERING

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INTRODUCTION TO GENETIC ENGINEERING
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Dictionary Definition Genetic Relating to
genes or inherited characteristics Engineering T
he design, construction and operation of
structures and machines, using scientific
principles
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Dictionary Definition
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• Genetic Engineering
• The technique of removing, modifying, or adding
  genes to a DNA molecule in order to change the
  information it contains. By changing this
  information, genetic engineering changes the type
  or amount of proteins an organism is capable of
  producing, thus enabling it to make new
  substances or perform new functions.
• The technology used to genetically manipulate
  living cells to produce new chemicals or perform
  new functions.
• The modification of the characteristics of an
  organism by manipulating its genetic material
  (DNA.)
• The science of changing the DNA of a plant or
  animal to produce desirable characteristics.
  Examples of desirable characteristics include
  fast growth and unusually large size.

Web Definitions


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Other Terms Genetic engineering genetic
modification (GM) gene splicing (older
term) "Transgenic organism" is now the preferred
term for genetically modified organisms with
extra-genome (foreign genetic) information, as
opposed to "genetically engineered" or
"genetically modified" organisms (which may refer
to changes made within the genome such as
amplification or deletion of genes). Background Da
niel Nathans and Hamilton Smith received the 1978
Nobel Prize in physiology or medicine for their
isolation of restriction endonucleases, which are
able to cut DNA at specific sites. Together with
ligase, which can join fragments of DNA together,
restriction enzymes formed the initial basis of
recombinant DNA technology.
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An iconic image of genetic engineering this 1986
autoluminograph of a glowing transgenic tobacco
plant bearing the luciferase gene of the firefly
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Genetic Engineering and Food The most commonly
engineered crops are canola, chicory, corn,
cotton, squash, tomatoes, and soy. Currently in
the US, 35 percent of all corn is genetically
engineered as well as 55 of all soy and cotton.
Although cotton is most commonly thought of as a
material, cottonseed oil is used in foods. Soy is
more widely consumed than many would think, as
60 of processed foods contain soy. Consumer
Reports of September 1999 shows that products
such as Boca Burgers, Jiffy Corn Mix, Ovaltine
Malt, Bravo Tortilla Chips, various infant
formulas, and Bac-Os Bacon Flavor Bits contain
genetically engineered ingredients.
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Nutritional effects No tests have been conducted
on the effects of genetically engineered food on
the human body. At this time, we could not do
longitudinal studies on people who are consuming
foods containing genetically engineered
ingredients because foods are not labeled. Thus,
it would be impossible to develop a control
group. One significant problem with genetically
engineered foods is the risk to people with
specific food allergies. For example, Brazil nut
genes were inserted into soybeans to increase
their protein content. The product was ready to
go to market when tests showed that the soybeans
caused allergic reactions in people with
allergies to Brazil nuts. In addition, new
allergens may be introduced into the food system
through genetic engineering.
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Why are crops genetically engineered?
Currently, 85 of genetically engineered crops
are engineered for herbicide or pest resistance.
The other 15 are engineered to be viral
resistant or have more "desirable traits" such as
increased oil content or shelf life. These
desired traits are not necessarily preferred by
or beneficial to the consumer, but they fit
within the framework of our industrialized,
concentrated agriculture system, which entails
large-scale production and long distance
transport.
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(Base)
The bases of DNA molecules carry genetic
information whereas their sugar and phosphate
groups perform a structural role.
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Nucleophilic attack of 3-OH terminus on the
innermost phosphorus of a deoxyribonucleoside
triphosphate
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It is important to understand that mutations can
arise from normal replication and from DNA
damage. Mutations arising from DNA replication
are caused by the fact that sometimes the DNA
polymerase inserts the wrong nucleotide (i.e a G
opposite a T or an A opposite a C etc)  thus
causing a mismatch. Mismatches are repaired by
the DNA mismatch repair system. This system
therefore repair replication errors. The
following table shows the number of errors made
by biological systems compared with human actions.
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Basic mechanism of DNA repair. The three steps
common to most types of repair are excision (step
1), resynthesis (step 2), and ligation (step 3).
In step 1, the damage is cut out by one of a
series of nucleases, each specialized for a type
of DNA damage in steps 2 and 3, the original DNA
sequence is restored by a repair DNA polymerase,
which fills in the gap created by the excision
events. DNA ligase seals the nick left in the
sugar-phosphate backbone of the repaired strand.
Nick-sealing, which requires energy from ATP
hydrolysis, remakes the broken phosphodiester
bond between the adjacent nucleotides. Some types
of DNA damage (deamination of cytosine, for
example) involve the replacement of a single
nucleotide, as shown in the figure. For the
repair of other kinds of DNA damage, such as
thymine dimers, a longer stretch of 10 to 20
nucleotides is removed from the damaged strand.
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DNA crossover.  (a) Two homologous pairs of
sister chromatids align side by side.  (b) The
two homologs are connected at a certain point 
called chiasma.  (c) The two homologs exchange
the DNA segment from the chiasma to the end of
chromosomes
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GENE A hereditary unit consisting of a sequence
of DNA that occupies a specific location on a
chromosome and determines a particular
characteristic in an organism. Genes undergo
mutation when their DNA sequence changes. Origin
of the word German Gen, from gen-, begetting, in
Greek words (such as genos, race, offspring).
GENOME  1. The set of genes carried by an
individual. 2. The set of genes shared by members
of a reproductive unit such as a population or
species.
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Illustration of the placement of genes in a
chromosome.
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Genes can be as short as 1000 base pairs or as
long as several hundred thousand base pairs. It
can even be carried by more than one chromosome.
The estimate for the number of genes in humans
has decreased as our knowledge has increased. As
of 2001, humans are thought to have between
30,000 and 40,000 genes.
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Promoter is the DNA region where the
transcription initiation takes place.  In
eukaryotes, the sequence of a promoter is
recognized by specific transcription factors.
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The most common promoter element in eukaryotic
protein genes is the TATA box, located at -35 to
-20.  Its consensus sequence is TATAAA. Another
promoter element is called the initiator (Inr). 
It has the consensus sequence PyPyAN(T/A)PyPy,
where Py denotes pyrimidine (C or T), N any,
and (T/A) means T or A.  The base A at the third
position is located at 1 (the transcriptional
start site). TATA box and initiator are the core
promoter elements.  There are other elements
often located within 200 bp of the
transcriptional start site, such as CAAT box and
GC box which may be referred to as
promoter-proximal elements
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