The Question is from neet-botany molecular-basis-of-inheritance , and it was created by the author K SURESH KUMAR

Question

What was the key observation in the Hershey-Chase experiment that supported DNA as the genetic material?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Hershey-Chase experiment and identification of genetic material
 **Related Topics**: DNA structure, bacteriophages, radioactive isotopes
 **Prerequisites**: Understanding of DNA and protein as potential genetic material, basic knowledge of radioactive labeling techniques.
## SOLUTION PATHWAY
**Given Information**:
  Hershey-Chase experiment used bacteriophages (viruses that infect bacteria) to determine whether DNA or protein was the genetic material.
  Bacteriophages were labeled with either radioactive phosphorus ($^{32}P$) to label DNA or radioactive sulfur ($^{35}S$) to label protein.
  The bacteriophages were allowed to infect bacteria.
**Method & Steps**:
 1. Determine which labeled material entered the bacterial cells.
  Reasoning: The genetic material should be transferred into the bacterial cell to direct the production of new viruses.
  Formula/Rule: None explicitly, but the experiment relies on the principle that radioactive isotopes can be used to track the location of molecules.
 2. Analyze the results of the experiment.
  Working:  The Hershey-Chase experiment showed that $^{32}P$ (associated with DNA) was found inside the infected bacterial cells, while $^{35}S$ (associated with protein) remained outside.
  Key Point: This demonstrated that DNA, not protein, entered the bacteria and was responsible for directing the synthesis of new viruses.
 3. Conclude which molecule is the genetic material.
  Result: The key observation supporting DNA as the genetic material was the presence of $^{32}P$ inside the bacterial cells.
  Verification: The experimental results strongly indicated that DNA carries the genetic information, leading to the conclusion that DNA is the genetic material.
 ## OPTION ANALYSIS
A :x: Radioactive sulfur ($^{35}$S) is associated with proteins, not DNA.  The experiment showed that it remained outside the bacterial cells.
B ✓: Radioactive phosphorus ($^{32}P$) is associated with DNA.  Its presence inside the bacterial cells was the key finding.
C :x: This contradicts the experimental findings; only $^{32}P$ was found inside the cells.
D :x: This would have implied that neither DNA nor protein were involved in heredity, which is incorrect.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the roles of $^{32}P$ and $^{35}S$:  Remembering that phosphorus is a component of DNA and sulfur is a component of proteins is crucial.
  2.Misinterpreting the results:  Understanding that the presence of the radioactive label inside the bacteria indicates the transfer of the genetic material is essential.
 **Quick Tips**:
  1.Remember the elements: Phosphorus in DNA, Sulfur in proteins.
  2.Visualize the experiment:  Imagine the labeled phage infecting the bacteria and where the radioactivity ends up.

K SURESH KUMAR · Answer

Radioactive sulfur ($^{35}$S) was found inside the bacterial cells.

K SURESH KUMAR · Answer

The correct Option is "Radioactive phosphorus ($^{32}$P) was found inside the bacterial cells."

K SURESH KUMAR · Answer

Both radioactive sulfur and phosphorus were found inside the bacterial cells.

K SURESH KUMAR · Answer

Neither radioactive sulfur nor phosphorus were found inside the bacterial cells.

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