2.2 All cells arise from other cells Flashcards
What is mitosis?
Parent cell divides = two genetically identical daughter cells, containing identical/exact copies of DNA of the parent cell.
- Stages - ‘PMAT’
What is interphase?
The nucleus has been artificially enlarged to make it easier to see what is going on. DNA & centriole have already been replicated during interphase.
G1?
- Cell that just divided
- Organelle synthesis, and cytoplasm increases in volume
S?
Semi conservative DNA replication
- Chromosomes replicated to form chromatids and new histones are synthesised
G2?
Further synthesis of proteins/organelles. Preparation for mitosis
Describe prophase:
The chromosomes condense. Original chromosome and its copy are chromatids. Joined to their copy at a centromere.
Centrioles migrate to opposite ends of the cell. Spindle fibres start to develop from each centriole. Membrane of the nucleus breaks down
Describe metaphase:
Chromosomes line up at the equator and attach to certain spindle fibres at their centromeres. No association between the homologous pairs in terms of the way they line up at the equator
Describe anaphase:
The sister chromatids split apart at the centromeres as they are pulled to opposite poles of the cell by spindle fibres
Describe telophase:
Spindle fibres break down and a new nuclear envelope forms around each group of chromosome
What is cytokinesis?
The cell constricts inwards from its middle until the cell physically splits into two separate cells. Each cell is an exact copy of its parents
Why is mitosis important in the life of an organism?
Parent cell divides to produce 2 genetically identical daughter cells for…
- Growth of multicellular organisms by increasing cell number
- Repairing damaged tissues / replacing cells
- Asexual reproduction
What does uncontrolled cell division lead to the formation of?
Malignant tumour – cancer – spreads and affects other tissues / organs
Benign tumour – non-cancerous
How do cancer treatments control rate of cell division?
Disrupt the cell cycle – cell division / mitosis slows – tumour growth slows
- Prevent DNA replication→prevent / slows down mitosis
- Disrupts spindle activity / formation → chromosomes can’t attach to spindle by their centromere → sister chromatids can’t be pulled to opposite poles of the cells → prevent/slow mitosis
:( Disrupt cell cycle of normal cells too, especially rapidly dividing ones e.g. cells in hair follicles
☺Drugs more effective against cancer cells because dividing uncontrollably / rapidly
What are some factors that cause cancer?
- Chemicals: tobacco (normally the genes switch on when their task is done. If tobacco carcinogens cause the genes to mutate to oncogenes which do not switch on, cells divide uncontrollably and cancers develop)
- Ionisation radiation (gamma and x-rays). They damage DNA causing mutations which may lead to the development of a cancer
What are some ways to treat cancer?
- Surgery: the cancer is removed
- Chemotherapy: drugs which block different stages of the cell cycle
- Radiotherapy: the cancer is bombarded and destroyed by a stream of particles emitted by a radioactive source
- Immunotherapy: some of the proteins which are part of the cell-surace membrnae
