the past, DNA was one of the most difficult molecule for the scientists to
analyze. Today the situation is completely different. DNA represent one of the
easiest macromolecule of the cell that can be analyzed. Scientists are able to
isolate unique region of a genome, to create indefinite number of copies of it,
and to resolve the sequence of its
nucleotides in a short amount of time. Genetic engineering has one of the
biggest impact on discovery of the whole new families of genes and proteins,
while revealing that a lot of proteins have been much more highly preserved in
evolution than had been suspected. Technices that are used today for
genetic engineering has given us the insight into many protein fuctions and
individual domains within proteins, which allowed scientist to find many
relationships between them1 .
represent a small region in side of DNA molecule and examining such small regions,
scientist developed techniques that enables to extract specific part of DNA.
First method discovered late in the 1960s by molecular biologists Werner Arber,
Hamilton O. Smith, and Daniel Nathans was using restriction enzymes2 .
These enzymes cut the DNA molecule at a specific place which is specifically defined
by nucleotide sequence, therefor cleaving the DNA into a small fragments2
. The length of DNA can be easily determined by gel electrophoresis.
DNA that containts specific gene can be cloned. Cloning is a process in which
we can produce multiple copies of a particular peace of DNA. There is a several
ways that gene cloning can be done, but
one of the most simpliest is include putting the DNA into a plasmid (Fig. 1).
The most used plasmid vectors for genetic engineering are double stranded DNA.
Recombinant plasmid is afterwards introduced into bacteria. Over the time
bacteria will grow and divide, making copies of DNA3 .Complementary DNA which is
produced from a single stranded RNA can be very poferfull tool. Some of the
reasons why scientist prefer to use cDNA instead of genomic DNA is because it
is free of introns (non-coding sequences), they can get more template, because
of the multiple copies of mRNA and less background sequence, because only
sequence expressed as mRNA will be present in cDNA. In this process enzyme
called reverse transcriptase is used which converts a single stranded RNA into
complementary DNA and using gene specific primers we can amplify the gene of
interest via PCR4 .