Discovery of DNA's structure and function Transitional Reasoning Download PDF

Questions

1. 1.

   In their classic 1952 blender experiment, Alfred Hershey and Martha Chase cultured T2 bacteriophages with either radioactive sulfur-35 or radioactive phosphorus-32 before allowing them to infect Escherichia coli cells. After agitating the infected cultures to detach empty viral coats and centrifuging the suspension, they analyzed the radioactivity in the resulting bacterial pellet and supernatant fluid. Based on the chemical composition of macromolecules and the physical separation of the components, which deduction accurately explains why the pellet contained predominantly phosphorus-32?

   • A) Sulfur is concentrated primarily in nucleic acids, demonstrating that viral protein enters the cell interior to deliver transcriptional instructions.
   • B) Phosphorus is contained in the nucleotide backbone of DNA rather than proteins, demonstrating that viral DNA enters the host cytoplasm to direct heredity.
   • C) Both sulfur and phosphorus enter the bacterial interior in equal amounts, establishing that genetic inheritance requires a co-dependent nucleoprotein complex.
   • D) Phosphorus is exclusive to the outer capsid proteins, confirming that structural proteins enter the host while nucleic acids remain outside.