When plants make flowers, gene A is expressedin whorls 1 and 2, gene B is expressed in whorls 2 and 3 and gene C in whorls 3 and 4; gene D in contrast is expressed in 2,3 and 4. What is predicted to be the consequence of homozygosity for a null mutation in gene C?

a) no sepals

b) no petals

c) no petals or sepals

d) no gametes

The correct answer would be option D) no gametes.

Explanation:

The ABC model of the flower was formulated to describe the collection of genetic procedures that determines floral organs in several plants. These species consist of four whorls which are sepals, petals, stamens, and carpels. These whorls are expressed by the expression of a number of genes present in each whorl or verticli.

Gene A is solely responsible for the sepals while the co-expression of A and B genes are responsible for the petals. The identity of the stamens is expressed by B and C and the carpels require C and D genes to be active.

The homozygousity for a normal mutation in gene C will lead to inactive or lack stamens and carpels, which are male and female reproductive organs. These are an important structure for forming gametes.

Thus, the correct answer would be option D) no gametes.