Question

In the apetala 2 mutant, sepals are replaced by carpel-like structures. Explain how that can happen on a molecular level.

Answer 1

There are 3 classes of homeotic genes A, B and C for flower development. That is formation of sepals, petals, stamen and carpel from flower mesistem.

APETALA 2 belongs to class A gene. It produces a transcription factor and responsible for sepal and petal formation from whorls 1 and whorls 2.

So mutatant APETALA 2 will allow AGAMOUS expression and will lead to the formation of carpel and stamen instead of sepals and petals. Actually presence of class A gene (APETALA 2) prevents expression of class C genes ( AGAMOUS) in the first two whorls.