A dish of animal cells was grown in the presence of radioactive phosphorous. The phosphorous largely ended up in nucleotides inside the actively growing animal cells. In which cellular structure or structures would you predict the majority of the radioactive phosphorous to accumulate?

Nucleus

Explanation:

Nucleotides serve as monomers for the synthesis of DNA and RNA in an actively growing cell. A growing cell undergoes the process of DNA replication and the nucleotides having radioactive phosphorus would be incorporated into the newly formed DNA strands. Since DNA is present in the nucleus of an animal cell, the radioactive phosphorus would end up in the nucleus of these cells. Nucleotides are also monomers for RNA and synthesis of RNA also occurs in nucleus. So, most of the radioactive P would be present in the nucleus.