Which of the following statements is correct?

Question

BlackTom AI · Accepted Answer

In this question, we need to evaluate each statement about bacterial conjugation and the F factor.
Option 1: 'The F factor helps bacteria reproduce more quickly.' This is not accurate as a general rule. The F factor is a fertility plasmid that enables transfer of DNA during conjugation, but it is not primarily described as accelerating bacterial reproduction; its main role is facilitating gene transfer, not increasing replication speed.
Option 2: 'An F+ cell transfers chromosomal genes to the recipient.' While an F+ cell can transfer the F plasmid itself to a recipient during conjugation, chromosomal gene transfer from an F+ donor is not the typical or defining feature. Chromosomal transfer is more characteristic of Hfr cells, where the F factor is integrated into the chromosome.
Option 3: 'An Hfr cell has the F factor integrated into the bacterial chromosome.' This statement is correct. In Hfr (high-frequency recombination) cells, the F factor is integrated into the bacterial chromosome, which enables transfer of chromosomal genes during conjugation, often into the recipient but not the entire chromosome.
Option 4: 'Conjugation with an Hfr cell usually converts the recipient cell to an F+ cell.' This is a common misconception. Conjugation with an Hfr donor typically results in transfer of some chromosomal DNA rather than establishment of a new F plasmid in the recipient; the recipient often remains F− unless it acquires the F factor separately, which is not implied by typical Hfr conjugation. In many cases, the transferred chromosomal DNA may integrate via homologous recombination, but the recipient does not automatically become F+.
Therefore, after evaluating all options, option 3 accurately describes the key concept about Hfr cells and the F factor integration.

Which of the following statements is correct?单项选择题

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