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?

• A. Rough endoplasmic reticulum
• B. The Golgi apparatus
• C. Rough endoplasmic reticulum and Golgi apparatus
• D. The Golgi apparatus and the nucleus
• E. The nucleus

Answer: (E)

Verified step by step guidance

1. Understand that phosphorous is a key component of nucleotides, which are the building blocks of nucleic acids like DNA and RNA.
2. Recognize that the nucleus is the cellular structure where DNA is housed and where RNA is synthesized, making it a primary site for nucleotide accumulation.
3. Consider the role of the nucleus in actively growing cells, where DNA replication and RNA transcription are occurring, requiring a high concentration of nucleotides.
4. Acknowledge that while other organelles like the rough endoplasmic reticulum and Golgi apparatus are involved in protein synthesis and processing, they are not the primary sites for nucleotide accumulation.
5. Conclude that the majority of radioactive phosphorous, incorporated into nucleotides, would accumulate in the nucleus due to its central role in nucleic acid metabolism.