Biology, Eighth Edition (Raven)

Chapter 28: Prokaryotes

Bacterial Conjugation

Is DNA replication required for conjugation? Conjugation is the direct transfer of DNA from one bacterial cell to another bacterial cell. The transferred DNA is a plasmid, a circle of DNA that is distinct from the main bacterial chromosome. The F plasmid is similar to a virus or a transposon in its ability to move independently of the main chromosome. The transfer of the plasmid take advantage of the complementary nature of double stranded DNA. One strand of the plasmid is transferred and the other remains in the original cell. Both strands have the complementary stranded added so that each cell ends up with a complete plasmid.

View the animation below, then complete the quiz to test your knowledge of the concept.


Arrange the following in the proper order in which they occur during bacterial conjugation.

1. DNA at the origin of transfer is cut
2. Relaxosome binds
3. Coupling factor binds
A)1, 2, 3
B)2, 1, 3
C)2, 3, 1
D)3, 2, 1
E)3, 1, 2

During bacterial conjugation, plasmid replication occurs in
A)the donor only.
B)the recipient only.
C)both the donor and recipient.
D)either the donor or the recipient, but not both.
E)neither the donor nor the recipient.

If a culture contains both F+ and F- cells, what is expected to happen over time?
A)No conjugation, because conjugation occurs only between cells that are F+.
B)No conjugation, because conjugation occurs only between cells that are F-.
C)All F+ cells will be converted to F-.
D)All F-cells will be converted to F+.
E)All cells will become genetically identical.

The pilus is found on both the donor and recipient cells.

The exporter pumps the T-DNA into the recipient cell, while leaving relaxase in the donor cell.
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