ABSTRACT
I. INTRODUCTION Cell division is one of the fundamental processes of growth and development of plants and animals. The time and place of cell division in an organism play a critical role in many developmental processes. The development of a complex organism with a defined form and structure requires tightly regulated cell growth and proliferation as well as transitions from cycling state to quiescent state and vice versa. In order to duplicate the genetic material and produce two daughter cells, the cell goes through a set of orderly events generally referred to as the cell cycle. The cell cycle consists of four distinct phases called gap1 (G1), synthetic phase (S), gap2 (G2), and mitosis (M). In the G1 phase cells prepare for S phase, during which DNA synthesis takes place and the cell replicates its chromosomes [1,2]. The completion of S phase leads into another gap phase (G2). Upon completion of G2, cells enter mitosis (M phase), where duplicated chromosomes segregate into two daughter cells [3]. However, it should be pointed out that in some rare instances cycling cells have only two phases (M and S) without intervening gap phases (G1 and G2). For example, the first 13 nuclear division cycles during Drosophila embryo development do not have any gap phases [4]. Similarly, nuclear division cycles during early endosperm development in plants seem to lack gap phases [5].
