Transduction: A Type of Recombination
The process of transduction is not a new process.
It is the phenomenon in which the DNA from one bacterium is transferred to other bacterium with the help of a viral vector.
Transduction can also be defined as a process by which a foreign DNA from a cell is introduced in other cell through a virus.
This is a very common process used by the molecular biologists for introduction of a foreign gene into the genome of the host.
Transduction was first carried out by Norton Zinder and Joshua Lederberg at the University of Wisconsin-Madison in 1951.
Viruses which infect bacteria are termed as bacteriophages.
When such bacteriophages infect a bacterial cell their prime function is to take the charge of replication, transcription and translation occurring in the host cell for their use and by doing this they produce a number of numerous virions or complete viral particles which harbor DNA or RNA and a protein coat.
Transduction can commence either through lytic cycle or lysogenic cycle.
If the lysogenic cycle is adopted then the chromosome of the bacteriophage is incorporated in the bacterial chromosome where it can remain dormant for thousands of generations.
If the lysogen is induced through some other means like UV radiation then the phage chromosome is erased from the bacterial chromosome and initiates the lytic cycle which results in the lysis of cell and release of the phage particles.
The lytic cycle is responsible for the production of new phage particles which are released by the lysis of the host cell.
The packaging of bacteriophage DNA has low reliability and small pieces of bacterial DNA along with small pieces of bacteriophage genome may become condensed together into the bacteriophage genome.
During the process of packaging some phage genes are left behind in the bacterial chromosome.
There are basically three modes of recombination processes that can lead to the incorporation of the bacterial DNA into the viral DNA and generating two types of transduction methods.
These methods are generalized and specialized transductions.
Generalized transduction can take place either by recombination or heedful packaging.
If the bacteriophage after entering into the bacterial cell takes the charge of the host cell's machinery for making viral particles then the lytic cycle will be followed but if by chance the bacterial chromosomal DNA is inserted into the viral capsid and a mistake occurs then the generalized transduction will commence.
If the virus replicates by using the heedful packaging it tries to fill its nucleocapsid with the genetic material.
Viral packaging mechanisms may also result in the generation of new viral particles.
The viral particle which is now loaded with the bacterial DNA infects other bacterial cell.
This bacterial material may get recombined with the gene of other bacterial cell upon infection.
If a new fragment of DNA is inserted into this recipient cell it can adopt three fates.
The DNA inserted may be absorbed or may be used in the case of emergency.
If the bacterial DNA that was inserted belongs to the category of plasmids then it will re-circularize and will become a plasmid again.
If the inserted chromosome is homologous with that of the recipient's chromosome then conjugation will take place.
This method of recombination is random and the amount of the genetic material recombined depends upon the size of the viral particle used.
The second category of the transduction is specialized transduction.
It is the result of mistakes that occur during the transition of lysogenic to lytic cycle of the virus.
If a virus removes itself from the bacterial genome incorrectly the bacterial DNA may get incorporated into the capsid of the virus.
There are also three fates of the specialized transduction.
The DNA can be absorbed or may be used at the time of emergency.
The bacterial DNA may match with the homologous chromosome of the recipient cell and may get exchanged.
A double copy of the bacterial genes may be formed.
The typical example of specialized transduction is λ phages in Escherichia coli.
Viruses that have RNA as their genetic material are unable to combine with DNA.
Transformation and transfection are also common techniques used for the insertion of DNA into a cell.
It is the phenomenon in which the DNA from one bacterium is transferred to other bacterium with the help of a viral vector.
Transduction can also be defined as a process by which a foreign DNA from a cell is introduced in other cell through a virus.
This is a very common process used by the molecular biologists for introduction of a foreign gene into the genome of the host.
Transduction was first carried out by Norton Zinder and Joshua Lederberg at the University of Wisconsin-Madison in 1951.
Viruses which infect bacteria are termed as bacteriophages.
When such bacteriophages infect a bacterial cell their prime function is to take the charge of replication, transcription and translation occurring in the host cell for their use and by doing this they produce a number of numerous virions or complete viral particles which harbor DNA or RNA and a protein coat.
Transduction can commence either through lytic cycle or lysogenic cycle.
If the lysogenic cycle is adopted then the chromosome of the bacteriophage is incorporated in the bacterial chromosome where it can remain dormant for thousands of generations.
If the lysogen is induced through some other means like UV radiation then the phage chromosome is erased from the bacterial chromosome and initiates the lytic cycle which results in the lysis of cell and release of the phage particles.
The lytic cycle is responsible for the production of new phage particles which are released by the lysis of the host cell.
The packaging of bacteriophage DNA has low reliability and small pieces of bacterial DNA along with small pieces of bacteriophage genome may become condensed together into the bacteriophage genome.
During the process of packaging some phage genes are left behind in the bacterial chromosome.
There are basically three modes of recombination processes that can lead to the incorporation of the bacterial DNA into the viral DNA and generating two types of transduction methods.
These methods are generalized and specialized transductions.
Generalized transduction can take place either by recombination or heedful packaging.
If the bacteriophage after entering into the bacterial cell takes the charge of the host cell's machinery for making viral particles then the lytic cycle will be followed but if by chance the bacterial chromosomal DNA is inserted into the viral capsid and a mistake occurs then the generalized transduction will commence.
If the virus replicates by using the heedful packaging it tries to fill its nucleocapsid with the genetic material.
Viral packaging mechanisms may also result in the generation of new viral particles.
The viral particle which is now loaded with the bacterial DNA infects other bacterial cell.
This bacterial material may get recombined with the gene of other bacterial cell upon infection.
If a new fragment of DNA is inserted into this recipient cell it can adopt three fates.
The DNA inserted may be absorbed or may be used in the case of emergency.
If the bacterial DNA that was inserted belongs to the category of plasmids then it will re-circularize and will become a plasmid again.
If the inserted chromosome is homologous with that of the recipient's chromosome then conjugation will take place.
This method of recombination is random and the amount of the genetic material recombined depends upon the size of the viral particle used.
The second category of the transduction is specialized transduction.
It is the result of mistakes that occur during the transition of lysogenic to lytic cycle of the virus.
If a virus removes itself from the bacterial genome incorrectly the bacterial DNA may get incorporated into the capsid of the virus.
There are also three fates of the specialized transduction.
The DNA can be absorbed or may be used at the time of emergency.
The bacterial DNA may match with the homologous chromosome of the recipient cell and may get exchanged.
A double copy of the bacterial genes may be formed.
The typical example of specialized transduction is λ phages in Escherichia coli.
Viruses that have RNA as their genetic material are unable to combine with DNA.
Transformation and transfection are also common techniques used for the insertion of DNA into a cell.
