Summary Edexcel GCSE Biology Topic 2 - Cells and Control
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Edexcel GCSE Biology Topic 1 - Key Concepts in Biology
Edexcel GCSE Biology Topic 3 - Genetics
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Mitosis
Mitosis is cell division to produce 2 genetically identical daughter cells It is important for
growth and repair of tissues. Cells are dying and being replaced all the time.
An animal had to undergo this to make mitosis occur:
• Enlarge
• More cytoplasm
• More organelles
• More protein
• Copy DNA
• More cell membrane
• A second nucleus
• Divide into 2
Interphase – The DNA in the cell is copied (making X-shapes, each containing a chromosome
in its copy). Sub-cellular parts (such as mitochondria) are also copied
Prophase – The membrane around the nucleus breaks down and spindle fibres appear
Metaphase – The chromosomes line up in the middle of the cell
Anaphase – Each of the chromosome X-shapes splits to form two single chromosomes. The
single chromosomes move away from one another
Telophase – The single chromosomes arrive at opposite ends of the cell. The membranes
around the nucleus start to form again
Cytokinesis – The cytoplasm of the cell is separated as a cell membrane divides the cell into
2 daughter cells
Diploid is a cell or organism that has paired chromosomes, one from each parent.
Clones are organisms that are exact genetic copies. Every single bit of their DNA
is identical. Clones can happen naturally—identical twins are just one of many
examples. Or they can be made in the lab.
,DNA replication is important during the interphase phase. In this the cell makes extra sub-
cellular parts (mitochondria). DNA replication also occurs to make copies of all the
chromosomes. The copies of the chromosome stay attached to each other, making it look
like X.
Asexual reproduction produces offspring that are clones, meaning vessels had the same
chromosomes as their parent (genetically identical). Therefore, asexual reproduction relies
on mitosis.
Stem Cells
A group of cells near the end of each shoot and root allows
plants to continue growing throughout their lives. These
groups are called meristems. The cells in meristems divide
rapidly by mitosis. Many of the cells then increase in length
(elongation) and differentiate into specialised cells that have
different functions.
Cells that can divide repeated over a long period of time to produce cells that can
differentiate are called stem cells. In plants, these cells are found in meristems (unspecialised
and found in tips of shoots and roots). Plant stem cells are usually able to produce any kind
of specialised cell throughout the life of the plant. This is not for most animals especially
vertebrates
A meristem is an area of
We have 3 different types of stem cells: the plant where rapid cell
• Pluripotent – differentiate into any specialised cell division happens. There are
• Multipotent – differentiate into many specialised cells normally found in the tips
• Unipotent – only differentiate into one specialised cell of shoots and roots.
Stem Cells are found in:
• Bone marrow (adult stem cells)
• Embryo (embryonic)
• Shoot tips (meristems)
Adult stem cells cannot differentiate into any other type of cell
,
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