Q.46 True breeding Drosophila flies with curved wings and dark bodies were mated with
true breeding short wings and tan body Drosophila.
The F1 progeny was observed to be with curved wings and tan body.
The F1 progeny was again allowed to breed and produced flies of the following phenotype:
45 curved wings tan body,
15 short wings tan body,
16 curved wings dark body, and
6 short wings dark body.
The mode of inheritance is
Options:
(A) Typical Mendelian with curved wings and tan body being dominant
(B) Typical non-Mendelian with curved wings and tan body not following any pattern
(C) Mendelian with suppression of phenotypes
(D) Mendelian with single crossover
Inheritance Pattern of Wing Shape and Body Color in Drosophila melanogaster
Drosophila melanogaster is a classical genetic model organism.
Analysis of F1 and F2 progeny ratios helps determine
whether traits follow Mendelian inheritance, linkage, or other non-Mendelian patterns.
Question Overview
A true-breeding Drosophila with curved wings and dark body
was crossed with a true-breeding fly having short wings and tan body.
- F1 progeny: Curved wings and tan body
- F2 progeny phenotypes:
- 45 curved wings, tan body
- 15 short wings, tan body
- 16 curved wings, dark body
- 6 short wings, dark body
Step 1: Identification of Dominant Traits
The F1 progeny show only curved wings and
tan body, indicating that:
- Curved wings are dominant over short wings
- Tan body is dominant over dark body
Step 2: Analysis of F2 Phenotypic Ratio
Total F2 progeny:
45 + 15 + 16 + 6 = 82
Expected Mendelian dihybrid ratio = 9 : 3 : 3 : 1
Expected values (approximate):
- 9/16 × 82 ≈ 46 → Curved, tan
- 3/16 × 82 ≈ 15 → Short, tan
- 3/16 × 82 ≈ 15 → Curved, dark
- 1/16 × 82 ≈ 5 → Short, dark
The observed data closely matches the expected Mendelian ratio.
Inference
The two traits assort independently and show complete dominance,
indicating a typical Mendelian dihybrid cross.
Correct Answer
Option (A): Typical Mendelian with curved wings and tan body being dominant
Key Takeaways
- F1 phenotype reveals dominance
- 9:3:3:1 ratio confirms Mendelian dihybrid inheritance
- No linkage or suppression is involved
Conclusion
The inheritance of wing shape and body color in this Drosophila cross
follows a typical Mendelian dihybrid pattern, with curved wings
and tan body as dominant traits. Hence, Option (A) is the correct answer.
