Switched on in the sepal and petal whorls - Gene A
Switched on in the petal and stamen whorls- Gene B
Switched on in the stamen and carpel whorls - Gene C
Explanation:
The mechanism of flower morphogenesis in Arabidopsis has been deduced through a genetic model called ABC model. The floral homeotic gene have been classified into 3 categories-A,B and C.
Genes from category A -APETALA 1 and APETALA2are expressed in petal and stamen primordia.
Genes from category B - APETALA 3 and PISTILLATA are expressed in petal and stamen primordia.
Genes of category C- AGAMOUS affect stamen and carpels.