MITOSIS AND MEIOSIS

1 EJC H2 Biology T2W10 Mitosis & Meiosis Cell Division – Mitosis & Meiosis 1. Overview of Topic The first single cellular organisms appeared about 3.5 billion years ago, roughly about a billion years after Earth was formed. It took a longer time for more complex life forms to evolve, with the first multicellular organisms only appearing about 600-800 million years ago. As life on earth progressed from single-cellularity to multi-cellularity, there was a need for the cell cycle to be more systemic and precise. Nuclear division is a stage of the cell cycle. Following nuclear division, the genetic information stored in the form of DNA, on chromosomes, is appropriately passed on to daughter cells from the parent cells. In mitosis, the daughter nuclei would possess the same type and number of chromosomes as the parent nuc lei. Meiosis occurs only in the sexually reproducing or ganisms. In meiosis, the daughter nuclei (haploid) end up with half the number of chromosom es as the parent cell (diploid). The daughter chromosomes may also have different allelic combinations due to allelic exchanges between the maternal and paternal chr omosomes. Mitosis and Meiosis bring about genetic stability and genetic variation in the organisms. In this chapter, we will be examining these nuclear division processes. 2. Learning Outcomes a. Describe the events that occur during the mitotic cell cycle and the main stages of mitosis (including the behaviour of chromosomes, nuclear envelope, cell membrane and centrioles). b. Explain the significance of the mitotic cell cycle (including growth, repair and asexual reproduction) and the need to regulate it tightly . (Knowledge that dysregulation of checkpoints of cell division can result in uncontrolled cell division and cancer is required, but detail of the mechanism is not required.) c. Describe the events that occur during the meiotic cell cycle and the main stages of meiosis (including the behaviour of chromosomes, nuclear envelope, cell membrane and centrioles). (Names of the main stages are expected, but no the sub-divisions of prophase.) d. Explain the significance of the meiotic cell cycle (including how meiosis and random fertilisation can lead to variation). 3. References Campbell, N.A. and Reece, J.B. (2008). Biology, 9th edition. Pearson. Jones & Jones. (1997). Advanced Biology. Hoh Yin Kiong (2003). Longman A-Level Course in Biology, Vol. 1. Longman Green, Stout and Soper (1990). Biological Sciences, Vol 1. Cambridge Raven, Johnson, Losos, Mason & Singer (2008). Biology, 8th edition. McGraw-Hill.

2 EJC H2 Biology T2W10 Mitosis & Meiosis Contents 1. Overview of Topic ................................ ................................ ................................ ...... 1 2. Learning Outcomes ................................ ................................ ................................ .... 1 3. References ................................ .