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Presented by wong lian sing, syazadamia, Lee jia jia and Siti noor fadhilah for subject Microbial Genetic
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Hfr Conjugation and Chromosomal Transfer
• Conjugation is the transfer of chromosomal material from one bacterial cell to another by direct cell-to-cell contact was discovered in 1946 by Lederberg and Tatum”,
(Adelberg & Pittard, 1965)
• F plasmid is a piece of DNA exist on its own in the cytoplasm.
• The F plasmid is considered to be an episome which may become integrated into the main chromosome.
• When the F genes become integrated into the chromosome, the cell is said to be Hfr (High Frequency of Recombination).
Hfr bacteria Possess the entire F episome integrated into the bacterial
genome.
F+ bacteria Possess F factor as a plasmid independent of the bacterial genome. The F plasmid contains only F factor DNA and no DNA from the bacterial genome.
F' (F-prime) bacteria Formed by incorrect excision from the chromosome, resulting in F plasmid carrying bacterial
sequences that are next to where the F episome has been inserted
F− bacteria Do not contain F factor and act as
the recipients.
The Hfr chromosome, originally circular, unwinds and is transferred to the F− cell in a linear fashion.(Griffiths et al,2000)
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References:
• Adelberg, E. A., & Pittard, J. 1965. Chromosome Transfer in Bacterial Conjugation. Bacteriological Reviews, 29(2), 161–172.
• Griffiths, A.J.F., Miller, J.H., Suzuki, D.T., et al.2000.Bacterial Conjugation. An Introduction to Genetic Analysis. 7th edition. New York,NY:W.H. Freeman. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK21942/
• Gross,J.D., Caro,L.G.1966. DNA transfer in bacterial conjugation. Journal of Molecular Biology. Volume 16,Issue 2,pp269-284.
• Friedrich Bonhoeffer. 1966. DNA transfer and DNA synthesis during bacterial conjugation. Zeitschrift für Vererbungslehre.Volume 98, Issue 2 , pp 141-149
• Sarathy,P.V., Siddiqi,O. 1973. DNA synthesis during bacterial conjugation: II. Is DNA replication in the Hfr obligatory for chromosome transfer? Journal of Molecular Biology. Volume 78, Issue 3,pp 443-451.
