Crossover Control: Homeostasis Essay -- Biology, Chromosome Engeneeri

Crossover Control: Homeostasis in Yeast Meiosis Control of formation of crossovers for proper chromosome segregation is governed by the crossover – non crossover ratio i.e., crossovers are formed at the expense of non crossovers; better known as the crossover homeostasis. Subject Terms: Meiosis, Crossover Control, Crossover Interference, Crossover Homeostasis Cell division is inevitable for the proper growth and development of any organism. While Mitosis helps in the somatic cell division, Meiosis acts in the germ cell for gametic division or gametogenesis. Meiosis starts with Prophase – 1 where the formation of crossover takes place. Crossovers are really important as they result into proper segregation and disjunction of chromosomes (Page and Hawley, 2003) and also, they bring about the variation in the species. Lack of crossover formation results into improper segregation and non-disjunction of chromosome and this results into aneuploidy, which can be detrimental for the organism. Thus, formation of crossovers in Meiosis is highly important. Upstream of crossovers are the double strand breaks (DSBs) that lead to the formation of crossovers (Keeney, 2001). The quality of double strand breaks to give rise to guaranteed crossover formation is known as obligate crossover or chiasma (Jones, 1984). For the accurate segregation of chro mosomes, it is highly necessary that there should be at least one double strand break hence at least one crossover formation per chromosome pair. Thus, formation of crossover is a tightly controlled and regulated event in Meiosis (Kleckner et al., 2004). This control is achieved by two important factors. First is the phenomenon of crossover interference in which the formation of one crossover affec... ...ion. These research statistics suggest that the work carried out by Martini et al. has definitely opened up a whole new field for research, and lots of work needs to be done to achieve valuable insight of the regulation of crossover control in meiosis. Several researchers are currently working on to unravel the mystery of the underlying molecular mechanism by which the regulation of crossover control takes place. Also, tremendous work needs to be done to propose the mechanism of crossover homeostasis with regards to crossover interference and the region specific differences arising in the HIS4LEU2 gene locus. Probably by using chromosome engineering we can further our understanding about this. Figure 2: Flow diagram explaining the control of crossover formation and regulation of meiosis through crossover homeostasis and crossover interference in S. cerevisiae.