4.4. Genetic Engineering
and Biotechnology
4.4.7 to 4.4.8
Part 2
4.4.7 State that, when genes are transferred between species,
the amino acid sequence of polypeptides translated from
them is unchanged because the genetic code is universal
• Genetic engineering refers to the deliberate
• It is possible to move genetic material between
species because the genetic code is universal.
This means that, for every organism, the same
RNA codon codes for the same amino acid in an
mRNA strand.
• UUU and UUC both code for the amino acid
phenylalanine while CUU, CUC, CUA, and CUG all
code for leucine, regardless of the species.
Genetic code is Universal
• Since the genetic code is universal, it is
possible to transfer genetic material from one
species to another. Because the code is
universal, it is possible to introduce a human
gene for making insulin into a bacterium.
• The bacterium will then produce the human
protein hormone insulin, which is responsible
for making cells take up more glucose and
convert it to glycogen.
Gene Transfer
• The technique of taking a gene out of one
organism ( the donor organism, e.g. a fish) and
placing it in another organism ( the host
organism, e.g. a tomato) is a genetic
engineering procedure called gene transfer.
• Such a transfer was done to make tomatoes
more resistant to cold and frost.
Gene Transfer
• It is possible to put one species’ gene into
another’s genetic make up because DNA is
universal. In the example of tomatoes, proteins
used by fish to resist the icy temperatures of
arctic waters are now produced by the modified
tomatoes to make them more resistant to cold.
• Another example of gene transfer is found in Btcorn, which has been genetically engineered to
produce toxins that kill the bugs which attack it.
• The gene, as well as the name come from a
soil bacterium, Bacillus thuringiensis, which
has the ability to produce a protein that is
fatal to the larvae of certain crop-eating pests.
Questions to Ponder
• Is it ethically acceptable to alter an organism’s genetic integrity?
• If the organism did not have the gene in the first place, could there
be a good reason for its absence?
• Why are people so worried about this new technology? In selective
breeding, thousands of genes are mixed and matched. With GMOs
only one gene is changed. Is that not less risky and dangerous than
artificial selection?
• Would strict vegetarians be able to eat a tomato which has a fish
gene in it?
• Does research involving GM animals add a whole new level to
animal cruelty and suffering in laboratories?
• If Bt—crops kill insects, what happens to the local ecosystem which
relies on the insects for food for pollination?
4.4.8 Outline a basic technique used for gene transfer involving
plasmids, a host cell (bacterium, yeast or other cell), restriction
enzymes (endonucleases) and DNA ligase
Gene transfer involves the following elements:
A vector
A host cell
Restriction enzymes
DNA ligase
The vector is what is needed to carry the gene into the host
cell. Plasmids are often used as vectors.
• Bacteria carry all the required genetic information on one
large circular DNA. However, most bacteria also possess
extra DNA in the form of plasmids. Plasmids are bits of
genetic material carrying 2-30 genes. Plasmids my replicate
at the time the chromose replicates or at toehr times.
Steps in cloning a gene
• Gene therapy video
Gene transfer in insulin production from abpi
The general technique of gene transfer
Technique of gene transfer
• Plasmids are used to clone a desired gene.
• First you splice or introduce a desired gene into a
plasmid and transfer it into a bacterial cell.
• Then, culture these bacteria; many of them will have
the plasmid with the desired gene.
• Use a section of nucleotides, complementary to the
desired gene, but also attached to a (radioactive) label
to find out which plasmids have the gene and which do
• Use restriction enzymes to cut the desired gene out of
the plasmids and purify the gen using gel
• The host cell is the cell which is to receive the
genetic material. A bacterium may be the host
cell and produce a protein desired by humans.
• Restriction enzymes (endonucelases) are used
to cut a desired section of the DNA. Bacteria
produce these enzymes naturally as a defense
against invading viruses.
• One commonly used restriction enzymes recognizes sequence
GATTC and cuts both strands of the DNA between G and A.
• When preparing to transfer DNA, the same restriction enzyme is
used for the host and the donor so the cuts are made in the same
• This way, the same ‘sticky ends’ are created so that the donor DNA
can fit in between the host DNA.
• The result is the uneven cut in the DNA and the ends of the DNA
are referred to as “sticky ends”. If the same sequence is found on
another section of DNA and is cut in the same way, the two strands
can be combined.
• To attach the two cut sections of DNA, the enzyme DNA ligase is
used to create the required covalent bonds.
Recombinant DNA

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