If 35S were found in progeny phages rather than 32P, which component would this indicate enters the host cell?

If 35S were found in progeny phages rather than 32P, which component would this indicate enters the host cell?

• A. RNA
• B. Lipids
• C. Phage DNA
• D. Phage protein

Answer: (D)

Radiolabeling experiments distinguish which phage component enters a host during infection. Phosphorus-32 marks nucleic acids (DNA and RNA), while sulfur-35 marks proteins because sulfur is present in amino acids like methionine and cysteine. If 35S shows up in progeny phages, it means the component that entered the host and was used to assemble new virions was protein, since only proteins would carry the 35S label. This indicates the phage protein itself entered the host cell. In contrast, 32P would indicate nucleic acids entered (typically phage DNA, the carrier of genetic information). Lipids wouldn’t carry the labels in this type of experiment, so they wouldn’t account for the appearance of either tag in progeny.

Radiolabeling experiments distinguish which phage component enters a host during infection. Phosphorus-32 marks nucleic acids (DNA and RNA), while sulfur-35 marks proteins because sulfur is present in amino acids like methionine and cysteine. If 35S shows up in progeny phages, it means the component that entered the host and was used to assemble new virions was protein, since only proteins would carry the 35S label. This indicates the phage protein itself entered the host cell.

In contrast, 32P would indicate nucleic acids entered (typically phage DNA, the carrier of genetic information). Lipids wouldn’t carry the labels in this type of experiment, so they wouldn’t account for the appearance of either tag in progeny.