The Question is from neet-botany , and it was created by the author D VINOD

Question

In the Hershey-Chase experiment, what crucial observation confirmed that DNA, and not protein, was the genetic material injected into bacteria by bacteriophages?

D VINOD · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
 **Primary Concept**: Hershey-Chase experiment and identification of genetic material
 **Related Topics**: DNA structure, bacteriophages, radioactive labeling
 **Prerequisites**: Understanding of DNA and protein composition, basic experimental design
## SOLUTION PATHWAY
**Given Information**:
  Hershey-Chase experiment used bacteriophages (viruses that infect bacteria) labeled with radioactive isotopes.
  Two isotopes were used: radioactive sulfur (³⁵S) to label proteins and radioactive phosphorus (³²P) to label DNA.
  The goal was to determine which molecule (DNA or protein) entered the bacteria and carried genetic information.
**Method & Steps**:
 1. Bacteriophages were allowed to infect bacteria.
  Reasoning: This allowed the transfer of genetic material from the phage to the bacteria.
 2. The phage ghosts (empty phage protein coats) were separated from the infected bacteria by centrifugation.
  Working: This step separated the outside phage material from the inside bacterial cells.
 3. The radioactivity of both the bacteria and the phage ghosts was measured.
  Key Point: The location of the radioactive isotopes indicated which molecule (DNA or protein) entered the bacteria.
 3. The results showed that ³²P (DNA) was found inside the bacterial cells, while ³⁵S (protein) remained outside.
  Result: This indicated that DNA was the genetic material injected into the bacteria by the bacteriophages.
  Verification: The experiment supported the hypothesis that DNA is the genetic material, not protein.
 ## OPTION ANALYSIS
A :x: Incorrect. This would indicate that protein was the genetic material.
B :x: Incorrect. This would suggest both DNA and protein were injected, contradicting the experimental results.
C :x: Incorrect. This would indicate that neither DNA nor protein entered the bacteria, which is impossible.
D ✓: Correct. This observation directly supports the conclusion that DNA, labeled with ³²P, was the genetic material transferred into the bacteria.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the isotopes: Remembering that ³⁵S labels proteins and ³²P labels DNA is crucial.
  2.Misinterpreting the results:  Understanding that the location of the radioactivity, not the amount, is key in determining which molecule was transferred.
 **Quick Tips**:
  1.Mnemonic:  'P' for Phosphorus and DNA, 'S' for Sulfur and Protein.
  2.Visualize the experiment: Imagine the phage injecting its material and then separation of the phage from bacteria.

D VINOD · Answer

Radioactive sulfur (35S) was found inside the bacterial cells, while radioactive phosphorus (32P) remained outside.

D VINOD · Answer

Both radioactive phosphorus (32P) and sulfur (35S) were found inside the bacterial cells.

D VINOD · Answer

Neither radioactive phosphorus (32P) nor sulfur (35S) were found inside the bacterial cells.

D VINOD · Answer

The correct Option is "Radioactive phosphorus (32P) was found inside the bacterial cells, while radioactive sulfur (35S) remained outside."

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