Transformation vs Transduction
Conjugation is a well-known method of DNA recombination, which can be found in both eukaryotes and prokaryotes. Later on scientists found that DNA can transfer from one bacterial cell to another by another two mechanisms; namely, transformation and transduction. Similar to conjugation, these two mechanisms transfer DNA in one direction and recombination occur between alleles in homologous DNA regions. Both mechanisms transfer very few amount of DNA and do not transfer the entire cell chromosome.
Transformation was first discovered in 1928 by Fred Griffith, a medical officer in the British Ministry of Health, London. It is the mechanism of which uptake of DNA fragments from the environment, passes and incorporates the same DNA fragments into the recipient’s chromosome. After the successful transformation, the recipient cell (transformant) has gained some ability it previously lacked. In prokaryotes like bacteria, transformation occurs regularly when the cells exist in great numbers, such as in human intestinal tract or in rich soil.
The ability of a cell to uptake extracellular DNA from the environment is called its competence. The competence depends on variable property among bacterial species. Transformation can be done artificially or sometimes it occurs naturally. If it occurs naturally, it increases the potential of causing disease more often.
Unlike the transformation, transduction requires a virus as an agent to carry DNA fragment from donor to recipient cell. The virus involving in this process is known as a bacteriophage. Like all viruses, the bacteriophages have a core of DNA or RNA surrounded by a coat of protein. There are two ways that bacterial cells can interact with phages; namely, lytic cycle and lysogenic cycle. In lytic cycle, viral phage penetrates a host cell, destroys host’s chromosome and replicates itself within the host cell. At the end, these phages destroy (lyse) the same host cell and hence called virulent phages. Unlike in lytic cycle, the direct lyse is not involved in lysogenic cycle. In lysogenic cycle, phage DNA integrates into the host chromosome as a prophage. After integration, the host cell undergoes DNA replication and binary fusion, thus results copies of host cell with prophages. Finally, these prophages will excuse themselves from hosts’ chromosomes and go to lytic cycle.
What is the difference between Transformation and Transduction?
• DNA transfer method of transformation is that the naked DNA moves across the wall and membrane of the recipient, whereas that of transduction is by a defective phage.
• In transformation, extracellular DNA fragments acquired while, in transduction, bacteriophage insert DNA fragment.
• Transformation use to acquire antibiotic resistance, whereas transduction does not.
• Transduction requires a virus as a host, whereas transformation does not.
• Plasmid transfer is possible in transformation whereas, in transduction, it is not likely to occur.
• Unlike transformation, transduction occurs in two ways; namely, lytic cycle or lysogenic cycle.