Figure 272 Depicts Changes to the Amount of DNA Present in in a Recipient

Multiple Choice

Figure 27.2 depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr-cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing-over occurs (i.e., a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA) . Use Figure 27.2 to answer the following questions.

Figure 27.2
-Which question, arising from the results depicted in Figure 27.2, is most interesting from a genetic perspective, and has the greatest potential to increase our knowledge base?

A) If reciprocal crossing-over could occur even if the piece of donated Hfr DNA is identical to the homologous portion of the recipient's chromosome, what prevents this from occurring?
B) Why do geneticists refer to the same structure by at least three different names: sex pilus, mating bridge, and conjugation tube? Why all the jargon?
C) What forces are generally responsible for disrupting the mating bridge?
D) How is it that a recipient cell does not necessarily become an Hfr cell as the result of conjugation with an Hfr cell?
E) What makes a cell an "Hfr cell"?