Hi, came across this question online.
Question 2. A cell is placed in a medium containing radioactively labeled thymidine. After the cells undergo replication three times, what percentage of the cells will have both strands of DNA labeled?
A. 25 percent
B. 50 percent
C. 75 percent
D. 100 percent
Answer: C is correct. This question asks you to determine the percentage of cells with both strands of DNA labeled after three replications of one cell in radioactive thymidine. After three rounds of replication, there will be eight cells: 2 3=8. After the first round, each cell will have one labeled strand and one not labeled. After the second round, two cells will have one labeled and one unlabeled strand, and two cells will have both strands labeled. After the third round, six cells will have both strands labeled. No matter how many rounds of replication occur, there will always only remain two cells that contain one labeled DNA strand and one unlabeled DNA strand.
Answer A is the percentage of cells that do not have both strands labeled; B and D are both the result of miscalculation.
i totally have no idea. how is it even possible to have any cells with both strands labelled? After the first replication, both cells have one labelled and one unlabelled strand (as the answer mention as well). After the second, wouldn't you have 4 cells with 2 cells having one unlabelled strand, and 2 cells having both labelled strands?
Appreciate the help!!
Question 2. A cell is placed in a medium containing radioactively labeled thymidine. After the cells undergo replication three times, what percentage of the cells will have both strands of DNA labeled?
A. 25 percent
B. 50 percent
C. 75 percent
D. 100 percent
Answer: C is correct. This question asks you to determine the percentage of cells with both strands of DNA labeled after three replications of one cell in radioactive thymidine. After three rounds of replication, there will be eight cells: 2 3=8. After the first round, each cell will have one labeled strand and one not labeled. After the second round, two cells will have one labeled and one unlabeled strand, and two cells will have both strands labeled. After the third round, six cells will have both strands labeled. No matter how many rounds of replication occur, there will always only remain two cells that contain one labeled DNA strand and one unlabeled DNA strand.
Answer A is the percentage of cells that do not have both strands labeled; B and D are both the result of miscalculation.
i totally have no idea. how is it even possible to have any cells with both strands labelled? After the first replication, both cells have one labelled and one unlabelled strand (as the answer mention as well). After the second, wouldn't you have 4 cells with 2 cells having one unlabelled strand, and 2 cells having both labelled strands?
Appreciate the help!!