Discussion
The diploid maize (2n = 2X = 20) treated with colchicine to induce tetraploidy. However, it showed sterility because :
Answer: C
The induced tetraploid was sterile because of problems in meiosis.
Colchicine blocks spindle formation, so the chromosomes double without the cell dividing. An autotetraploid has four homologous copies of each chromosome, and at meiosis these can pair as quadrivalents, trivalents plus univalents, or bivalents in various combinations. Irregular segregation then produces gametes with unbalanced chromosome numbers (aneuploid gametes), many of which are not viable, so fertility falls sharply.
Mitosis is not the problem: the tetraploid plant grows normally, and indeed its cells are often larger. Male sterility and self-incompatibility are specific genetic systems controlling pollen function or self-pollination; they are not the general cause of sterility in newly induced polyploids.
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