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Genetically engineered insulin:
Insulin is a polypeptide, consisting of 51 amino acids. The DNA code for the polypeptide is
very small (less than 200 bases long). This makes it difficult to find in a genome of 300 million
Instead, specialised centrifugation methods are used to separate mRNA for the insulin gene
from pancreas tissue.
Reverse transcriptase is used to synthesise a complementary DNA strand for the mRNA.
DNA polymerase and a supply of DNA nucleotides are added to the strand, copying the DNA
strand. The DNA strand is called a cDNA gene.
Unpaired nucleotides are added to give sticky ends.
Plasmids are then cut open with a restriction enzyme and mixed with the cDNA genes.
Some of the plasmids take up the gene.
DNA ligase then seals up the plasmids, which are now called recombinant plasmids because
they contain the new piece of DNA.
The plasmids are then mixed with bacteria, some of which take up the plasmids.
The bacteria are then grown on an agar plate, where each bacterial cell grows to produce a
mound of identical cells.
The development of Golden Rice:
A lack of vitamin A, retinol, in the diet causes health problems to many people in developing
countries. Vitamin A is required for the formation of the visual pigment rhodopsin,
responsible for the reception of light energy by rod cells in the retina of the eye. Vitamin A
deficiency can therefore cause night blindness.
Retinol can also be made from carotene, an orange pigment found in plant foods such as
People who eat diets based on rice many get insufficient amounts of retinol or carotene.
Genetically engineered golden rice contains carotene.
Genes (phytoene synthetase, from daffodil plants and Crt enzyme 1 from the soil bacterium
Erwinia uredovora) are inserted into rice plants so that the amount of carotene made by
the plants is increased and would be expressed by their seeds.
Golden rice is said to be biofortified because it contains higher than normal concentrations of
a particular nutrient ( carotene)
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Golden rice has also been cross-bred with natural rice varieties and the results show that
they could produce 3-4 times more carotene thank golden rice.
Human organs are in short supply and many people die each year while waiting for an organ
to become available.
One solution to the shortage is to use organs from animals (xenotransplantation).
Pig organs are often used because they have a similar size and structure to human organs.…read more