Mitosis •Large cells have a reduced SA:Vol ratio •Growth of organism •Replace dead, damaged or infected cells •Asexual reproduction |
Stages of the cell cycle
•interphase –G1: growth, protein synthesis, increase in the number of mitochondria and/or chloroplasts –S: DNA replication –G2: growth, protein synthesis, preparation for mitosis/cytokinesis •mitosis = nuclear division –prophase –metaphase –anaphase –telophase •cytokinesis = cellular division |
Mutations and Cancer
•Mutation = random changes to the base sequence of genes –A mutation may change a proto-oncogene (produces normal cell cycle control) which causes uncontrolled cell cycle and accumulates old and new cells to form a tumor •Mutagens = agents that produce changes in genes involved in controlling the cell cycle, causing uncontrolled cell division. –Chemical (asbestos, dioxins, tobacco smoke, etc.) –X-rays or short-wave UV light •Metastasis = movement of cells from a primary tumor to set up secondary tumors in other parts of the body. |
TOK: A number of scientific discoveries are claimed to be incidental or serendipitous. To what extent might some of these scientific discoveries be the result of intuition rather than luck?
When scientists obtain actual samples of their studies, they want to learn as much as possible about them, so they experiment and explore the results of every small change that they made. What probably happen during the discoveries of these experiments was that the scientist was playing around with cell division, and after twitching the system so that the cell would stop dividing correctly, then the tumour was formed.
When scientists obtain actual samples of their studies, they want to learn as much as possible about them, so they experiment and explore the results of every small change that they made. What probably happen during the discoveries of these experiments was that the scientist was playing around with cell division, and after twitching the system so that the cell would stop dividing correctly, then the tumour was formed.