Question

How many of the following genotypes possibly represent normal wings in Drosophila?
 (i) \( Vg^+Vg^+ \) 
(ii) \( Vg^+Vg^{ni} \) 
(iii) \( Vg^+Vg^{no} \) 
(iv) \( Vg^+Vg^{st} \) 
(v) \( Vg^+Vg \) 
 

• A. (i), (ii), and (iii) only
• B. (i) and (ii) only
• C. Only (i)
• D. (i), (ii), (iii), (iv), and (v)

Hint:

When evaluating phenotypes, ensure at least one dominant allele is present for the dominant phenotype to express. Homozygous recessive combinations always result in recessive phenotypes.

Answer 1

The Correct Option is D

In Drosophila, the normal wing phenotype is determined by the presence of at least one dominant \( Vg^+ \) allele. The recessive alleles \( Vg^{ni}, Vg^{no}, Vg^{st}, Vg \), etc., cause abnormal wing development only when present in homozygous recessive combinations.

 Step 1: Evaluate each genotype. \( Vg^+Vg^+ \): Both alleles are wild type, so the wings are normal. 

Normal wings. \( Vg^+Vg^{ni} \): One dominant \( Vg^+ \) allele is sufficient for normal wings. 

Normal wings. \( Vg^+Vg^{no} \): One dominant \( Vg^+ \) allele is sufficient for normal wings. 

Normal wings. \( Vg^+Vg^{st} \): One dominant \( Vg^+ \) allele is sufficient for normal wings. 

Normal wings. \( Vg^+Vg \): One dominant \( Vg^+ \) allele is sufficient for normal wings. 

Normal wings. Step 2: Count the genotypes. All five genotypes contain at least one dominant \( Vg^+ \) allele and hence represent normal wings. \[ \text{Genotypes representing normal wings} = (i), (ii), (iii), (iv), (v). \] Thus, the correct answer is: \[ \mathbf{(D) \ (i), (ii), (iii), (iv), \text{and} (v)}. \]