4 Cell division
4.1 Overview
Introduction DUMMY
In this unit you will learn how we are able to replicate our cells through the process of
cell division calledmitosis. Mitosis is absolutely vital to the survival of all organisms, as
without it unicellular organisms would not be able to reproduce and multicellular organisms
would not be able to grow or heal after damage. However, uncontrolled mitosis can result
in cancer, a potentially fatal condition. In this chapter we will review the stages of mitosis
in plants and animal cells. We will then discuss how cancer is caused and some treatments
that are available.
Key concepts- The cell cycle is divided into two main stages: interphase and the mitotic phase.
- During interphase cells grow in size and replicate their DNA.
- Chromosomes are present in the nuclei of all cells and consist of two chromatids joined
by a centromere. - Mitosis is the process by which cells distribute their replicated DNA to two daughter
cells. - The mitotic phase consists of five stages: prophase, metaphase, anaphase, telophase
and cytokinesis. - Mitosis is the means of reproduction in unicellular organisms that undergo asexual
reproduction. - Mitosis is required for growth and repair in multicellular organisms.
- Cancer is a disease of uncontrolled mitosis.
- Cancer is caused by carcinogens and is treated through surgery, radiation and chemother-
apy.
4.2 The cell cycle
Thecell cycleis the series of events that takes place in a cell that results in DNA replication
and cell division. There are two main stages in the cell cycle. The first stage isinterphase
during which the cell grows and replicates its DNA. The second phase is themitotic phase
(M-Phase) during which the cell divides and transfers one copy of its DNA to two identical
daughter cells. Figure 4.1 provides a brief overview of what takes place during each of the
key events of the cell cycle.98 4.1. Overview