Question

Study the following and identify the correct statements:
I. The alleles I{A} and I{B} regarding blood groups are dominant over I{O}, and I{A} and I{B} are co-dominant.
II. In some fishes, reptiles and birds, females are heterogametic (ZW) and males are homogametic (ZZ).
III. Genic balance theory states that Y-chromosome is essential for determination of sex in male Drosophila.
IV. Person with O blood group are called universal donors because their RBC contain both antigens A and B.

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

Hint:

Remember ZW/ZZ in birds; ABO dominance/co-dominance rules; sex determination in Drosophila depends on X:A ratio.

Answer 1

The Correct Option is A

• I is correct: I{A} and I{B} are both dominant over I{O}; I{A} and I{B} are co-dominant with each other.
• II is correct: in birds (and some reptiles/fish) females are ZW (heterogametic) and males ZZ (homogametic).
• III is incorrect: genic balance theory relates X:autosome ratio, not presence of Y — Y is not essential for male Drosophila (it carries male fertility genes but sex is determined by X:A ratio).
• IV is false: O group individuals lack A and B antigens (that's why they are universal donors), but the statement incorrectly says their RBC contain both antigens — wrong.
• Therefore correct statements are I, II → option (1).