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Which of the following statement(s) is/are true in regards to F+ x F- mating events?

  • A.DNA is transferred from F- to F+ cells
  • B.DNA is transferred from F+ to F- cells
  • C.No DNA is transferred because F- cells are unable to perform conjugation
  • D.No DNA is transferred because F+ cells are unable to perform conjugation

Answer: B

Correct answer: DNA is transferred from F+ to F- cells

In an F+ × F− mating the DNA moves from donor to recipient - from F+ to F−. The F+ cell makes the sex pilus, contact is established, and one strand of the F plasmid is nicked at oriT and transferred; both cells then synthesise the complementary strand, so the recipient becomes F+.

Transfer is therefore one-way, defined by which cell carries the F factor. The F− cell is not incapable of conjugating - it is a perfectly good recipient - it simply lacks the plasmid that encodes the machinery, so it cannot act as donor.

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