Question

Match List I with List II 

Choose the correct answer from the options given below: 
 

• A. A-IV, B-I, C-II, D-III
• B. A-IV, B-I, C-III, D-II
• C. A-IV, B-III, C-I, D-II
• D. A-I, B-IV, C-II, D-III

Hint:

Remember the standard points: 1.0 = Female and 0.5 = Male.
Anything between these two is an Intersex.
Ratios below 0.5 are Super males and ratios above 1.0 are Super females.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question is based on the Genic Balance Theory of sex determination proposed by C.B. Bridges in Drosophila melanogaster.
This theory states that sex is determined by the ratio between the number of X chromosomes ($X$) and the number of haploid sets of autosomes ($A$).

Step 2: Key Formula or Approach:
The Sex Index is calculated using the formula:
\[ \text{Sex Index} = \frac{\text{Number of X chromosomes}}{\text{Number of sets of autosomes (A)}} \]
Detailed Explanation:

• Sex Index of 1.0 (A-IV): When the ratio is 1.0 (e.g., $XXAA$), the phenotype is a normal fertile Female.

• Sex Index of 0.5 (B-I): When the ratio is 0.5 (e.g., $XAA$), the phenotype is a normal fertile Male.

• Sex Index of 0.67 (C-II): When the ratio falls between 0.5 and 1.0 (e.g., $XXAAA$ giving $2/3 \approx 0.67$), the organism shows characteristics of both sexes and is termed an Intersex.

• Sex Index of 0.33 (D-III): When the ratio is less than 0.5 (e.g., $XAAA$ giving $1/3 \approx 0.33$), the phenotype is a Super male (metamale), which is usually sterile and weak.

• Additional Note: A ratio greater than 1.0 (e.g., 1.5 from $XXXAA$) results in a Super female (metafemale).
Final Answer:
Matching the indices gives A-IV, B-I, C-II, and D-III.
This corresponds to option (A).