The figure below 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 (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).
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Which two processes are responsible for the shape of the curve at Time B?
A) transduction and rolling circle replication of single-stranded Hfr DNA
B) entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA
C) rolling circle replication of single-stranded Hfr DNA and activation of DNA pumps in the plasma membrane
D) transduction and activation of DNA pumps in the plasma membrane

Question

The figure below 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 (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). 
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Which two processes are responsible for the shape of the curve at Time B?
A) transduction and rolling circle replication of single-stranded Hfr DNA 
B) entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA 
C) rolling circle replication of single-stranded Hfr DNA and activation of DNA pumps in the plasma membrane 
D) transduction and activation of DNA pumps in the plasma membrane

Quizplus · Accepted Answer

The shape of the curve at Time B is the result of two processes: the entry of single-stranded Hfr DNA into the recipient cell and the rolling circle replication of the single-stranded Hfr DNA. This leads to a steady increase in the amount of DNA present in the recipient cell. Transduction and activation of DNA pumps in the plasma membrane are not involved in this process and therefore not the best choices.

The Figure Below Depicts Changes to the Amount of DNA