Question

Starting from a single cell which undergoes DNA replication, followed by cell division. One of the two cells formed further replicates its DNA. Which of the following is true for second generation daughter cells?

• A. One of the cells will contain DNA consisting of one strand from the original cell.
• B. One of the cells will contain DNA consisting of two strand from the original cell.
• C. Both of the cells will contain DNA consisting of one strand from the original cell.
• D. Both of the cells will contain DNA consisting of two strand from the original cell.
• E. Neither of the cells will contain DNA consisting of strands from the original cell.

Answer 1

The correct option is A One of the cells will contain DNA consisting of one strand from the original cell.

DNA replication is semi-conservative which refers to the synthesis of new DNA molecules, each with one new strand and one parental strand. If the original cell had DNA strands BB (imaginary), the two daughter cells will have one strand from original cell and one newly synthesized strand (BB’). According to the question, one of these two daughter cells (BB’) undergoes DNA replication. One of the two second generation cells will receive B strand of the original cell while other will get B’ strand. Hence, one of the second generation cells will have BB” DNA strand and other will have B’B” DNA. Thus, one of the two second generation cells will have one DNA strand of the original cell.

Therefore, the correct answer is option A.