Why are the recombinants produced from an Hfr x F⁻ cross rarely, if ever, F⁺?

Klug 12th Edition
Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages
Problem 10Describe the role of heteroduplex formation during transformation.
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Key Concepts
Heteroduplex Formation
Transformation
Genetic Recombination
Describe the origin of F' bacteria and merozygotes.
In a transformation experiment, donor DNA was obtained from a prototroph bacterial strain (a⁺b⁺c⁺), and the recipient was a triple auxotroph (a⁻b⁻c⁻). What general conclusions can you draw about the linkage relationships among the three genes from the following transformant classes that were recovered?
Explain the observations that led Zinder and Lederberg to conclude that the prototrophs recovered in their transduction experiments were not the result of F⁺ mediated conjugation.
Define plaque, lysogeny, and prophage.
Two theoretical genetic strains of a virus (a⁻b⁻c⁻ and a⁺b⁺c⁺) were used to simultaneously infect a culture of host bacteria. Of 10,000 plaques scored, the following genotypes were observed. Determine the genetic map of these three genes on the viral chromosome. Decide whether the interference was positive or negative.