THE BASIS FOR TRANSGENIC
ORGANISMS
TRANSFORMATION
The incorporation of a piece of
naked DNA (not attached to cells)
from one organism into the DNA of
another organism. The result is a
transgenic organism.
Why does genetic engineering work?
What do you know about the genetic code?
• The sequence of nucleotide bases on a DNA
molecule makes up the genetic code. Each triplet of
three bases codes for a particular amino acid.
• Using this code, a cell can produce any one of the
many proteins that it requires.
• One of the many remarkable features of the genetic
code is that it is universal; the three bases code for
the same amino acid whether it is in a bacterial cell
or a cell from another organism.
So what opportunity does this create?
• A gene taken from one organism should then
be able to produce exactly the same product if
it is introduced into another organism.
• This is the basis of genetic engineering, the
production of new characteristics by the
insertion of a gene from one organism.
• Genetic engineering has paved the way for
many biotechnology products in medicine,
agriculture, environmental products and
industrial applications.
Transgenic Organisms
– Transgenic Microorganisms
• Transgenic bacteria produce important substances
useful for health and industry. Transgenic bacteria have
been used to produce:
– insulin
– growth hormone
– clotting factor
Copyright Pearson Prentice Hall
The basic principles
A number of different techniques are used: What stages
are needed?
1. The isolation of the desired gene required to
produce the product, (How can we do this?)
2. Insertion of this foreign gene into the DNA of a host
cell by using a suitable DNA carrier called a vector,
(What is meant by suitable?)
3. Checking to find the host cells which contain the new
gene, (How do we know? Think antibiotic resistance)
4. Multiplying or cloning the organism containing the
new gene to produce large numbers of genetically
identical cells or organisms for commercial
Transgenic Organisms
– Transgenic Plants
• Transgenic plants are now an important part of our food
supply.
• Many of these plants contain a gene that produces a natural
insecticide, so plants don’t have to be sprayed with pesticides.
Copyright Pearson Prentice Hall
– Transgenic Animals
• Transgenic animals have been used to study genes and
to improve the food supply.
• Mice have been produced with human genes that make
their immune systems act similarly to those of humans.
This allows scientists to study the effects of diseases on
the human immune system.
• Transgenic animals are also becoming useful
commercially. On February 6, 2009 the US FDA
approved the first human biological drug produced
from such an animal, a goat. The drug, Atryn, is an
anticoagulant which reduces the probability of blood
clots during surgery or childbirth. It is extracted from
the goat's milk
Copyright Pearson Prentice Hall
Restriction endonucleases or restriction
enzymes: A little history
• In the early 1970s, researchers discovered restriction
endonucleases in bacterial cells.
• These enzymes are now known to be part of the natural
defense system of bacteria against bacterial viruses.
• They cut the virus DNA into small fragments and stop the
infection process.
• There are many different types of restriction enzymes, each
one cutting the DNA at a specific nucleotide sequence.
• Some cut the DNA straight across. Others produce a
staggered cut; a sequence of unpaired bases called “sticky
ends”.
• These are very important as they can join with
complementary sticky ends on other pieces of DNA.
Production of
sticky ends and
recombinant
DNA
Plasmids as
Vectors
Transformation needs
•Antibiotic resistance
gene
•Gene of interest
•Replication site
incorporated in the
plasmid for successful
transfer of a trait
Bacteriophage (virus) as
vectors
Sticks to the surface of the cell and injects genetic information into bacteria
The viral genes make more bacteriophages in the bacteria using the bacterial
DNA
This leads to destruction of the bacterium
When the bacteria split open, viruses burst out
YEAST ARE ANOTHER GOOD VECTOR
Examples
Glow mice: the jellyfish gene which causes them
to glow is inserted into the mouse’s sperm
before that sperm fertilizes the egg
Chimeric Mouse