Which of the following floral whorls are absent in agamous (ag) mutant of Arabidopsis?
Which of the following floral whorls are absent in agamous (ag) mutant of Arabidopsis?
Select an option to attempt
Correct Answer: Option B
Explanation
ABC (Homeotic gene) model of flower organ identity: Three classes of genes (A, B, C) acting in overlapping domains determine floral organ identity. A alone → sepals; A+B → petals; B+C → stamens; C alone → carpels. A and C are mutually exclusive (A represses C and vice versa). AGAMOUS (AG) provides C function in Arabidopsis (inner two whorls: stamens and carpels). In agamous (ag) loss-of-function mutants: C activity is lost; the mutual repression fails and A expands into all whorls. Without C: whorl 3 (normally B+C = stamens) becomes B+A = petals; whorl 4 (normally C = carpels) becomes A = sepals. Result: ag flowers are sepal-petal-petal-sepal... inflorescence (indeterminate, repeating). Stamens and carpels are ABSENT from ag mutants.