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Cell cycle Regulation
Document describes cell cycle regulation and the different phases in detail but simple language which is easy to understand for A level students and university student.
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DNADNA Cell Cycle
In the cell cycle, there are different phases which are G1, S,
G2 (Interphase).
G1 (GAP1) - In the G1 phase, we make more organelles,
because we don’t have enough organelles for 2 cells
therefore we need more. We synthesise more proteins and
enzymes to help with the replication of the DNA. And we
also repair any thymidine dimers as we don’t want to enter
the synthesis phase with any mistakes.
G1 / S Checkpoint – there is a checkpoint here and this is to make sure there are no
mistakes within the cell and we have enough organelles, proteins and enzymes before we
continue to the next stage of the interphase.
S - In the S (Synthesis) phase, DNA replication occurs and it is
maintained by DNA Polymerases (enzymes). We take the DNA
(genetic material) and open it up and form a replication bubble.
We synthesise new DNA base upon what bases we have in the
opened gap. Making a whole new strand.
G2 (GAP2) – In this stage, we need to make sure that the cell is big
enough before it enters mitosis. Therefore the main function of the
G2 phase is cell growth by increasing the cytoplasm and the
organelles.
G2 / M Checkpoint – The checkpoint between G2 and Mitosis has
the role of preventing cells to enter mitosis when DNA is
damaged. It gives the opportunity to repair and stop the proliferation of the damaged
cells.
G1 & S & G2 = Interphase.
After the interphase, we enter mitosis.
, DNA
The second stage of the cell cycle is called the M Phase (Mitosis)
When we were going through Interphase, the DNA within the nucleus was loose. In order
for us to be able to separate the DNA properly, we need a condensed DNA chromosomes
not loose DNA.
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
5. Cytokinesis
*Can be remembered as PMAT
1. Prophase – Chromosomes condenses and the nuclear envelope dissolves.
Microtubule organisation centres (MTOC) start to form.
2. Metaphase (M Remember as middle) – The microtubule organisation centres will
move to different ends of the cells. They have microtubules facing the
chromosomes. The microtubules are now connected to the chromosomes. The
chromosomes line up in the middle (on the metaphase plate).
M checkpoint - There is a checkpoint here making sure the chromosomes have all lines up
properly.
3.
Anaphase (A Remember as Away) – Chromosome is separated. Each chromosomes go
to each side (46 go to each). They are moved by the motor proteins.
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