Plasmids may also replicate by

Plasmids may also replicate by - to undergo rolling circle...

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Plasmids may also replicate by bi-directional or uni-directional replication normally during the same time period that the chromosomal DNA is undergoing replication. In this way, vertical transmission of plasmids (from parent to progeny) can also occur. Transfer of plasmids by conjugation would be an example of horizontal transmission. Another property of F+ plasmids is that they may occasionally integrate into the bacterial chromosome and behave as though they were part of the chromosome. Bacterial cells which contain an integrated plasmid are termed: Hfr males Hfr stands for high frequency of recombination . These males can undergo conjugation when mixed with F- female bacteria. As conjugation begins, the entire bacterial chromosome (with integrated plasmid) begins
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Unformatted text preview: to undergo rolling circle replication. It takes 90-100 minutes for an entire bacterial chromosome to undergo rolling circle replication and normally mating cells break apart (the conjugation tube breaks) before the entire displaced strand can cross. Thus the F- cell receives a large fragment of the bacterial chromosome and a small functionless fragment of the F plasmid. The F- bacterium remains F- {and would only become F+ if the entire chromosome + plasmid crossed the conjugation tube}. At a high frequency, homologous recombination occurs between the bacterial chromosome and the introduced DNA....
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