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Restriction enzymes:

  • are endonucleases which cleave DNA at specific sites

  • make DNA complementary to an existing DNA or RNA

  • cut or join DNA fragments

  • are required in vectorless direct gene transfer.


are endonucleases which cleave DNA at specific sites

Restriction enzymes are endonucleases which cleave DNA at specific sites. They are extracted from the bacterium E.coli.

Restriction enzymes Type I bind to a recognition site of a duplex DNA and cleave one strand only. Restriction Enzyme Type II are more valuable in gene manipulation and cleave the duplex at specific target sites at or near the binding site.


Hybridoma technology is used to :

  • kill the cancer cells

  • formation of somaclonal antibodies

  • formation of somatic hybrids

  • formation of antibiotics


formation of somaclonal antibodies

Monoclonal antibodies are usually produced from hybridoma clones. Each hybridoma clone is derived by the fusion of a rnyeloma cell and an antibody producing lymphocyte.


Assertion : In recombinant DNA technology, human genes are often transferred into bacteria (prokaryotes) or yeast (eukaryote).

Reason : Both bacteria and yeast multiply very fast to form huge populations which express the desired gene.

  • If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

  • If both Assertion and Reason are true but the Reason is not the correct explanation of the assertion

  • If Assertion is true but Reason is false.

  • If both Assertion and Reason are false


If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

In recombinant DNA technology, prokaryotic E. coli and eukaryotic yeast is the widely used host for replication and amplification of recombinant DNA. They replicate very fast in order to form a large population that express a desired gene.

Yeast artificial chromosome (YAC) is an important cloning tool for the analysis of complex genome such as that of humans. They allow the maintenance, propagation and analysis of such genome in an experimentally tractable system.


e -DNA is formed from m-RNA by which enzyme:

  • restriction endonuclease

  • reverse transcriptase

  • DNA polymerase

  • RNA polymerase


reverse transcriptase

C-DNA or complementary DNA is formed from m-RNA by the enzyme reverse transcriptase and the process of formation of C-DNA on the template of m-RNA is called C-DNA. It is formed through reverse transcription and is shorter than the actual or in- vivo gene because of the absence of introns and other non-coding regions.


cDNA probes are copied from the messenger RNA molecules with the help of

  • restriction enzymes

  • reverse transcriptase

  • DNA polymerase

  • adenosine deaminase


reverse transcriptase

Reverse transcriptase is an enzyme used by retroviruses to from complementary DNA (cDNA) from their RNA. The resulting DNA is then inserted into the chromosome of the host cell.

Restriction anzymes is an enzyme produced chiefly by certain bacteria, that has the property of cleaving DNA molecules at or near a specific sequence of bases.

DNA Polymerase is an enzyme that synthesizes DNA molecules from deoxyribonucleotides, the building blocks of DNA.

Adenosine deaminase is an enzyme which catalyzes the deamination of adenosine to inosine.


Introduction of foreign genes for improving genotype is

  • biotechnology

  • vernalization

  • tissue culture

  • genetic engineering


genetic engineering

Genetic Engineering is the introduction of foreign genes for improving genotype. It is a technique of manipulating prokaryotic and eukaryotic DNA. It allows breaking of a DNA molecule at two desired places to isolate a specific DNA segment and then its insertion in another DNA molecule at a desired position. The product thus obtained is called r DNA and the technique as genetic engineering.


Restriction endonuclease

  • cuts the DNA molecule randomly

  • cuts the DNA molecule at specific sites

  • restricts the synthesis of DNA inside the nucleus

  • restricts the synthesis of DNA inside the nucleus


cuts the DNA molecule at specific sites

Restriction endonuclease is a type of enzyme that can cleave molecules of DNA at a particular site called Restriction site having polindromic sequence. These enzymes are produced by many bacteria and protect the cell make leaving and destroying the DNA of invading viruses.  Now a days, restriction enzymes are widely used in the techniques of genetic engineering.


Kohler and Milstein developed biotechnology for :

  • monoclonal antibodies

  • steroid synthesis

  • immobilization of enzymes

  • myeloma


monoclonal antibodies

Monoclonal antibodies are monospecific antibodies that are made by identical immune cells that are all clones of a unique parent cell.

In 1975, Georges Kohler and Cesar Milstein succeeded in making fusions of myeloma cell lines with B cells to produce hybridomas that made antibodies to known antigens. These are pure, high affinity antibodies, specific for an antigen which are obtained outside the body from clonal cultures of hybridoma cells.


A tumor inducing plasmid widely used in the production of transgenic plants is that of

  • Escherichia coli

  • Bacillus thuringiensis

  • Staphylococcus aureus

  • Agrobacterium tumefaciens


Agrobacterium tumefaciens

Transgenic plants are plants that have been genetically engineered. It is a breeding approach that uses recombinant DNA techniques (RDT) to create plants with new characteristics.They are commonly identified as GMO or Genetically Modified Organisms. Agaraobacterium tumefaciens consists of Ti plasmid. It possess T- DNA which is responsible for causing tumour in host plant.


What is the first step in the Southern Blot technique

  • Denaturation of DNA on the gel for hybridization with specific probe

  • Production of a group of genetically identical cells

  • Digestion of DNA by restriction enzyme

  • Isolation of DNA from a nucleated cell such as the one from the scene of crime


Isolation of DNA from a nucleated cell such as the one from the scene of crime

The first of these techniques developed was the Southern blot, named after Dr. Edwin Southern who developed it to identify specific DNA sequences. Southern blotting is a detection technique used to find the target DNA sequences in the DNA sample in the field of molecular biology. The process starts from electrophoresis of DNA molecules which are hybridized in a blotting membrane followed by a transfer step where DNA from gel is transferred onto the blotting membrane.