Question

Suppose that you performed a version of the Hershey and Chase experiment, this time using 32P-labeled viruses that insert their double-stranded DNA into the DNA of the cells that they infect. The viral DNA is then treated as part of the cell's own DNA and is replicated during DNA replication and passed onto daughter cells when the cell divides. You infect a population of cells with the 32P-labeled viruses, and then let the infected cells go through two generations of cell divisions. If you then examine the cells, you should find 32P-labeled DNA in ____ of the cells.

Answer 1

After infecting cells with 32P-labeled viruses and allowing two generations of cell division, 32P-labeled DNA should be found in half of the cells due to semi-conservative DNA replication.

Step-by-step explanation:

When you infect a population of cells with 32P-labeled viruses and then let the infected cells go through two generations of cell divisions, we must consider how DNA replicates and is passed on to daughter cells. As DNA replication is semi-conservative, each new cell will receive one original (labeled) and one new (unlabeled) strand of DNA after the first division. After two divisions, assuming no errors or mutations, each cell will have either one strand of 32P-labeled DNA (from the first generation cells that had one labeled and one unlabeled strand) or no labeled DNA (from the first generation cells that had two unlabeled strands).

Therefore, after two rounds of cell division, the 32P label will be distributed among all four possible combinations of daughter cells. Specifically, after the first division, all cells will have 32P-labeled DNA, but after the second division, only half of the resulting cells will contain 32P-labeled DNA because each cell divides into two, with only one inheriting the labeled DNA template. As a result, you should find 32P-labeled DNA in half of the cells after two generations of cell division.

Answer 2

1/2 of the cells.

Step-by-step explanation:

DNA replication is a semiconservative process which means that one strand of each of the two DNA double helices formed after one round of DNA replication is the parental strand and the other one is the newly formed strand.

Given that a population of the cells was infected with 32P-labeled viruses which would insert its DNA into the host cell's DNA, after one generation of cell division, the 32-P labeled DNA would be present in one strand of all the DNA molecules present in all the cells.

After the second generation of cell division, the 32-P labeled parental strand would be present in 1/2 of the total cells while the rest half of the cells would have only the normal DNA.