Use the following information and graph to answer the 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).

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

Use the following information and graph to answer the 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).

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 graph shows an increase in the amount of DNA present in the recipient cell, indicating that DNA from the Hfr cell is entering the recipient cell. This process involves the entry of single-stranded Hfr DNA. The shape of the curve at Time B is due to rolling circle replication of the single-stranded Hfr DNA within the recipient cell, which leads to a rapid increase in the amount of DNA present. Therefore, the correct answer is B, entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA. The other options do not accurately describe the processes occurring during Hfr cell conjugation. Transduction is a different mechanism of DNA transfer that does not involve conjugation. Activation of DNA pumps in the plasma membrane is not a known process in Hfr cell conjugation.

Use the Following Information and Graph to Answer the Question