A culture of human tissue is being grown in a lab to study mitosis. A solution containing radioactively labelled cytosines was added to the culture in the middle of prophase, and then growth was halted at the end of telophase.

Where would the scientists see radioactively labelled DNA?

A. In the mother cells only-not in the cells produced at the end of telophase
B. Only in the nuclei of half the cells
C. In the cells produced at the end of Telophase-only in the daughter cells
D. In the nuclei of every cell
E. Nowhere in the cells

The cell cycle is an ordered set of events leading to cell growth and division into two daughter cells. The stages are G1-S-G2 (which comprise the interface of the cycle) and M. During the interface, the cell grows and synthesizes components necessary for survival (during G1 and G2), and duplicates its DNA (during S). And during M (Mitosis), the division of the nucleus into two daughter nuclei, and division of the cytoplasm occurs (the latter in a process called cytokinesis).

So, mitosis is the actual cell division, producing two genetically identical daughter cells. Each cell is diploid and contains the same number of chromosomes, because the genetic material was previously duplicated during S stage in interphase.

The stages of mitosis consist of :

Prophase: The chromosomes move from the lax working form to the compact transport form. The nuclear envelope is fractionated into a series of tanks that are no longer distinguishable from the ER. The nucleoli also disappear, dispersing in the cytoplasm in the form of ribosomes.

Metaphase: The mitotic or achromatic spindle appears, formed by beams of microtubules; the chromosomes join some microtubules through a lamellar protein structure located on each side of the centromere, called cinetochorus.

Anaphase: The offspring centromeres are separated from the chromatids, which now become offspring chromosomes. Each set of daughter chromosomes migrates to one pole of the cell. The mitotic spindle is the structure that carries out the distribution of the offspring chromosomes in the two offspring nuclei. The movement is carried out thanks to the activity of the chromosomal microtubules, which are shortened at the end attached to the cinetochorus. The polar microtubules slide in the opposite direction, distancing the two groups of child chromosomes.

Telophase: Begins when the chromosomes reach the poles of the cell. The offspring chromosomes lengthen, lose condensation, the nuclear envelope is formed again from the rough RE.

Cytosine is one of the five nitrogenous bases that make up the nucleic acids (DNA and RNA) and is represented in the genetic code by the letter C. The other four bases are adenine, guanine, thymine and uracil.

If the labeled cytosine is added during the prophase of mitosis, the DNA has already been duplicated during the S-stage and will no longer incorporate this labeled base into the molecule. So is not going to be found in either the mother cell or the daughter cells.