Introduction, types, explanation of each type, applications. For 12th, M.Sc, B.Sc students.

2. Transduction
 Transduction, a process of genetic recombination in bacteria in which genes from a
host cell (a bacterium) are incorporated into the genome of a bacterial
virus (bacteriophage) and then carried to another host cell when the bacteriophage
initiates another cycle of infection.
OR
 Transduction is the bacteriophage-mediated transfer of iDNA from an infected
cell to a recipient cell. Bacteriophages (or simply phages) are bacterial viruses
which pick up and transfer genes that are advantageous to their microbial host.
 It was given by scientists in 1952 by Norton Zinder and Joshua Lederberg.
Hershey and Chase used transduction as a tool to confirm that DNA is the genetic
material. Bacterial transduction occurs through generalized and specialized
transduction.
 The process of transduction was first studied in the bacterium Salmonella.

3. They can transfer both chromosomal and plasmid DNA. To achieve a stable bacterial
transduction, the translocated DNA must be incorporated into the recipient chromosome
by homologous recombination. It has been observed that some phages have a wide range
of bacterial hosts and can move across different species .
Phages first attach to their bacterial host and inject their genome.
Then, the injected genome seizes the host’s molecular machinery to synthesize
new phages.
Finally, new phages lyse the host cell and spread to the environment.

5. Types
The transduction in bacteria occurs in two
ways, either through a lytic or lysogenic cycle,
depending upon the type packaging of the viral
genome. :
•Generalized Transduction – In this, the phage can carry any
part of DNA.
•occur by lytic cycle.
•Specialized Transduction – In this, the phage carries only
the specific part of DNA.
•occur only through the lysogenic cycle, i.e. by temperate
phage.

6.  Cell lysis is a process in which a cell is
broken down or destroyed as a result of
some external force or condition.
A virus, when it infects a host cell, has two
possible life cycles through which it can move.
Depending on the environmental conditions and
various other factors, it can decide which of them
it wants to select – the lytic or lysogenic life
cycle.
 lysogeny - the condition of a host bacterium that has
incorporated a phage into its own genetic material; "when a
phage infects a bacterium it can either destroy its host or be
incorporated in the host genome in a state of lysogeny".
lysogenicity.

8. Generalized Transduction
• Any random part of DNA gets packed in bacteriophages by mistake
along with the viral genome. It occurs at the lytic stage of the phage
life cycle.
• When the virus-containing bacterial DNA infects another cell, it can
get inserted into the host genome or if it was a plasmid, then it can
reform the plasmid.
• Use - to study linkage information, gene mapping, comparing
genomes of two different bacteria, mutagenesis, etc.
• Example of generalized transduction includes E.coli transduction by
P1 phage.
Process
It includes the following steps:

9. 1.Firstly, the bacteriophage attacks the bacterial cell (donor cell).
2.The bacteriophage injects its genetic material, which then penetrates the
bacterial chromosome.
3.The phage DNA then controls the host cell machinery. This cause the
degradation of the bacterial chromosomal DNA, which results in small
fragments of the genetic material.
4.The replication of phage DNA occurs. At the time of packaging, the genetic
material of the bacterial DNA accidentally gets into the bacteriophages by a
phenomenon called “False packaging”.
5.Then, the biosynthesis of bacteriophages occurs, and the phages get to
assemble and finally cause lysis of the donor cell.
6.The bacteriophages then attack the other bacterial cell (recipient cell), and
again it will penetrate its phage DNA into the host cell.
7.The phage DNA will incorporate in the recipient’s DNA and leads to the
formation of a recombinant cell.

10. Specialized Transduction
• Here, only the specific part of the bacterial DNA is packed into the virus. It
occurs when viral DNA(prophage), inserted into the bacterial genome in
the lysogenic cycle.
• When prophage excises from bacterial DNA, some parts of bacterial DNA,
also excised. Here, the newly packed phage genome consists of both
bacterial and viral genome.
• Later, when the virus with the recombinant genome infects a new
bacterial cell, the bacterial gene also gets inserted into the host genome
with the viral genome through lysogeny. The recipient cell now shows
the newly acquired characteristics.
• Used for - Specialized transduction is commonly isolation and insertion of
genes of choice.
Example of specialized transduction includes E.coli transduction by 𝝀 phage.
Process
It includes the following steps:

11. 1.First, the bacteriophage attack the bacterial cell or donor cell.
2.Then, the genetic material of the bacteriophage will penetrate the bacterial
chromosome.
3.The phage DNA will incorporate within the bacterial DNA and then it will
start the replication cycle.
4.The phage DNA then control over the cell machinery of the bacteria. This
cause the assembly of the bacteriophages that consist of both phage and
donor’s DNA.
5.After that, a UV-light induces cell lysis and results in the release of
lysogens.
6.Then, the bacteriophages attack the other bacterial cell (recipient cell). This
bacteriophage will penetrate the prophage DNA into the recipient cell.
7.The phage DNA and the donor cell DNA will incorporate in the recipient’s
DNA, which leads to the formation of the recombinant cell.

12. Application of Transduction
Transduction is one of the most important tools for genetic engineering.
•Transduction is used to insert the genes of choices in animals and plant
cells to modify the genetic constituents and get the desired
characteristics.
•It can be used for gene therapy. It has huge potential to cure genetic
diseases.
•It is an important tool in genetics and molecular biology research.