BOTANY Higher Secondary Second Year - Textbooks Online

4. BIOTECHNOLOGY
In the science of genetics, some sweeping changes are taking place.
A lowly bacterium that is found in the bowels of everyone namely
Escherichia coli is drawing the attention of all scientists and learned people.
This bacterium has become one of the potentially most powerful tools
known to science in genetic manipulation In this chapter, you will learn
that we now have the ability to find specific genes, to cut them away from
chromosomes, to insert them into the chromosomes of other species. Genes
have been duplicated countless times to harvest their protein product in
large quantities. There are both advantages and disadvantages in doing
recombinant research on plants. Several important species such as carrot,
cabbage, citrus and potatoes can be grown from single cells. So, once a
gene is introduced to a cell, a clone of that cell can produce countless
altered progeny. Most plant characteristics that need improvement such
as growth rate, size of edible parts and amino acid balance are polygenic
– controlled by many genes. Most of the genes responsible for such traits
were not yet identified. It is also very difficult to clone five or more genes
which control a trait. These inevitable disadvantages are there in
recombinant DNA technology.
4.1. Recombinant DNA technology
It is a technique where the selected DNA of one organism
(Donor) is introduced to combine with the DNA of another organism
called recipient organism. As a result, the recipient organism acquires
the genetic abilities of the donor. Altering the genome of an organism
by introducing genes of interest is known as gene manipulation or
DNA recombinant technology. As this mechanism has the ability to
engineer new organisms, it is known as genetic engineering.
Basic techniques of genetic engineering
Bacterial cells have different kinds of enzymes. Some of these
can cut DNA into fragments and others can join such fragments. For
example, restriction endonucleases discovered in 1970 are involved in
cutting DNA at specific sites. Hence they are called molecular scissors.
The enzyme DNA ligase discovered in 1966 acts like a paste molecule
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