Cell cycles Flashcards
(12 cards)
what is Interphase
Interphase consists of three parts: the first growth phase (G1-phase), synthesis phase (S-phase and second growth phase (G2-phase).
the importance of cell division
The number of cells increases by mitosis enabling organisms to grow from a single cell to a complex multicellular organism.
Cells are constantly lost and replaced by new ones in the body.
Mitosis is important so that organisms can grow and repair damaged tissues.
Some organisms such as the hydra use mitosis to produce genetically identical offspring. The process is known as budding. Mitosis is also the method by which yeast cells multiply. This is called asexual reproduction.
Define prophase
Prophase
During prophase the chromatin network condenses to form visible chromosomes with chromatids. The nuclear membrane and nucleolus disappear. The centrioles move towards opposite sides of the cell (called the poles). Spindle fibres form between the centrioles to make the spindle apparatus.
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define metaphase
Metaphase
During metaphase the chromosomes line up on the equator (the mid-line between the poles). Spindle fibres attach to the centromeres on each chromosome.
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define anaphase
Anaphase
During anaphase, the centromere of each chromosome divides in two and the two chromatids of each chromosome split apart. Unreplicated chromosomes move to opposite poles. At the same time, cytokinesis typically begins.
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define telophase
Telophase
During telophase, the unreplicated chromosomes are now at the poles and the nuclear membrane and nucleolus forms around them. The spindle disappears. Cytokinesis occurs with cell cleavage in animals or a cell plate that forms in plants at the equator.
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difference between telophase in animals vs. plants
In animal cells a ring of filaments begin to contract around the centre of the dividing cell. Like a drawstring it pinches the cell in half. Each daughter cell receives about half of the cell membrane and cytoplasm (including the mitochondria and other organelles).
In plant cells that have a rigid cell wall, the cells cannot pinch in half. Rather a cell plate forms along the equator between the two daughter nuclei. The cell wall eventually forms into a new cell wall between the two daughter cells.
difference between benign & malignant tumours
Benign tumours
Benign tumours do not penetrate surrounding tissues and are usually enclosed in a capsule.
These usually grow quite slowly and don’t spread to other parts of the body. They usually have a covering made up of normal cells. Benign tumours are made up of cells that are quite similar to normal cells. They only cause a problem if they: grow very large, become uncomfortable or painful, are visible and unpleasant to look at, press on other body organs, take up space inside the skull (such as a brain tumour) or release hormones that affect how the body works.
Malignant tumours
These tumours spread between the cells of the tissues, damaging them.
These usually grow faster than benign tumours. They spread into surrounding tissues and cause damage. They also may spread to other parts of the body (called metastasis).
What is Metastasis
Metastasis is when cancer cells break away from the original site of growth and are spread by circulation of blood and lymph to other parts of the body.
Causes of cancer?
Cigarette smoke
Sun (UV radiation)
Radiation (e.g. x-rays)
Chemicals and pollutants (e.g. food additives, asbestos)
Hormonal imbalances
Certain viruses (e.g. HPV)
Genetic mutations/predispositions
Cures for cancer?
Surgery: tumours are physically removed
Radiation: kill cancer cells with targeted radiation
Chemotherapy: kill cancer cells with chemicals
Biological/Targeted therapy: e.g. use vaccines or bacteria to stimulate the body’s immune system to act against cancer cells.
What is cytokinesis
Karyokinesis separates the nucleus to each daughter cell but the process of cytokinesis is required to divide the cytoplasm. This usually begins during anaphase or telophase.
