#2.2.1
Within multicellular organisms, not all cells retain the ability to divide.
#2.2.2
Eukaryotic cells that do retain the ability to divide show a cell cycle.
- DNA replication occurs during the interphase of the cell cycle.
- Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.
#2.2.3
The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. The role of spindle fibres attached to centromeres in the separation of chromatids.
#2.2.4
Division of the cytoplasm (cytokinesis) usually occurs, producing two new cells.
#2.2.5
Meiosis is covered in section 4.3
#2.2.6
Students should be able to:
- recognise the stages of the cell cycle: interphase, prophase, metaphase, anaphase and telophase (including cytokinesis)
- explain the appearance of cells in each stage of mitosis.
#2.2.7
Mitosis is a controlled process. Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division.
#2.2.8
Binary fission in prokaryotic cells involves:
- replication of the circular DNA and of plasmids
- division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
#2.2.9
Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles.
#2.2P2
Required practical 2
Preparation of stained squashes of cells from plant root tips; set-up and use of an optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index.
Students should measure the apparent size of cells in the root tip and calculate their actual size using the formula:
\(\text{actual size} = \dfrac{\text{image size}}{\text{magnification}}\)