Question

Arrange the following concepts/principles chronologically from the oldest to the latest. 
• [(A).] Gene-for-gene hypothesis 
• [(B).] Dominance hypothesis 
• [(C).] Transforming principles 
• [(D).] Concept of heterosis 
Choose the correct answer from the options given below: 
 

• A. (C), (A), (B), (D)
• B. (C), (D), (A), (B)
• C. (B), (D), (C), (A)
• D. (B), (D), (A), (C)

Hint:

Key historical associations to remember:
- Dominance hypothesis: Davenport (1908).
- Coined "Heterosis": Shull (1914).
- Transforming principle: Griffith (1928).
- Gene-for-gene model: Flor (1942).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Developing genetic theories required key insights into the mechanisms of inheritance, gene function, molecular biology, and host-pathogen interactions.

Step 3: Detailed Explanation:
Let us review the historical dates for each concept:
1. Dominance hypothesis of heterosis (B): Proposed by Charles Davenport in 1908, this hypothesis suggests that heterosis (hybrid vigor) results from the masking of harmful recessive alleles in a heterozygote by dominant alleles.
2. Concept of heterosis (D): George Shull coined the term "heterosis" in 1914 to replace the phrase "heterozygosis", describing the increased vigor of a hybrid relative to its parents.
3. Transforming principle (C): Frederick Griffith conducted his famous experiments with Streptococcus pneumoniae in 1928, demonstrating that genetic information could be transferred between bacterial cells.
4. Gene-for-gene hypothesis (A): Harold Flor proposed this hypothesis in 1942 to explain the genetic relationship between host resistance and pathogen virulence, based on his studies of flax rust.
Arranging these concepts from oldest to latest:
\[ \text{Dominance hypothesis (B)} \rightarrow \text{Concept of heterosis (D)} \rightarrow \text{Transforming principle (C)} \rightarrow \text{Gene-for-gene hypothesis (A)} \] This corresponds to the sequence (B) \(\rightarrow\) (D) \(\rightarrow\) (C) \(\rightarrow\) (A).

Step 4: Final Answer:
The correct chronological sequence is Option (C).