Final answer:
Chromosomal DNA is transferred from Hfr cells to F- cells, where recombination can occur. Hfr cells have the F plasmid integrated into their chromosome, and during conjugation, they can transfer part of their chromosomal DNA to F- cells, introducing new genetic information.
Step-by-step explanation:
The question relates to the process of bacterial conjugation, which is a method of genetic material transfer among bacteria. The correct answer is that chromosomal DNA is transferred from Hfr cells to F- cells, where recombination occurs. Hfr cells, or High-frequency recombination cells, are those in which the F (fertility) plasmid has integrated into the bacterial chromosome. When Hfr cells conjugate with F- (F-minus) cells, a portion of the Hfr cell's DNA, starting at the site where the F plasmid has integrated into the bacterial chromosome, is transferred to the F- cell.
The DNA transfer begins with the formation of conjugation tube or sex pilus between the Hfr cell and the F- cell. During this process, the DNA is cut at the origin of transfer and the single-stranded DNA is then transfer into the F- cell. Conjugation is often incomplete, and typically only part of the Hfr genome is transferred into the F- cell. This DNA can then recombine with the F- cell's chromosome, potentially introducing new genetic traits.