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Resub for unit 11B assignment
D2- Evaluate how the behaviour of the chromosomes leads to variation
- Evaluate the significance of chromosomal behaviour during cell division
Mitosis
Interphase- before mitosis can occur the cell goes through the interphase which makes
the cell expand and duplicate its DNA.
– what is the significance of this happening? – what happens if it doesn’t occur
Interphase is significant in cell division because it helps the cell to grow, replicate its
DNA and then finalise for cell division preparations. This is important because if
interphase did not happen, then the cell would not be able to grow to its full size which
in return would not all for replication of its DNA and thus mitosis could no longer occur.
If mitosis did not occur, then there would not be any cell growth or cell reproduction,
and this means that genetic information cannot be passed on to the offspring which
would make variation in organisms impossible.
Prophase- in prophase the DNA and proteins in the nucleus (chromatin) compresses.
The chromatin coils and therefore becomes more compact. This results in the
development of visible chromosomes.
Prophase is significant in mitosis during cell division because it allows for the
alteration of the chromosomal shape which allows the chromosomes inside the
nucleus to move more easily around the cell, this is important because this movement
of chromosomes allows for each daughter cell to contain an exact copy of the parent
DNA cell. If prophase did not occur, then the cell would not be identical and if they are
not identical cells then genetic diseases could occur such as cystic fibrosis. Also, if the
cell is not identical then mutations of cells could form which could result in cancers
forming which can become fatal.
Metaphase- As they align in the middle of the dividing cell, the chromosomes
condense and become different to one and another.
Metaphase is a significant step during cell division as the metaphase checkpoint
occurs during this step. This is an important step during cell division because it checks
the cell to ensure that it is ready to divide making sure there is no mistake during the
process, as if this step fails or does not occur then it would prevent anaphase from
occurring, as they will not move properly to the poles during anaphase, even if one
single chromosome is out of alignment on the equatorial plate and if anaphase does
not occur then the cell is unable to duplicate thereby creating daughter cells. If there
is no duplication, then the cell will die.
, Anaphase- Each chromosomal pair is divided into two identical, independent chromosomes. The mitotic
spindle is a structure that separates the chromosomes during the anaphase.
Anaphase is a very significant stage during cell division as it ensures that the
duplicated DNA, duplicated during the interphase or S phase, is separated into
two equal sets, this happens due to the mitotic spindle which separates the sister
chromatids at the same times at their centromeres. If this step fails or does is
done incorrectly, for instance the sister chromatids being pulled to one side of the
pole, then it could result in nondisjunction which can cause the cells to be never
spilt apart thus not creating new cells, but only one larger cell. If this occurs then
the cell most likely would die as it has to many chromosomes in its nucleus,
however it can cause genetic conditions such as down syndrome where the
person has an extra copy in the chromosome 21.
Telophase- To isolate the nuclear DNA from the cytoplasm, a nuclear membrane
develops around each set of chromosomes. The chromosomes start to uncoil, making them more spread
and less compact.
Telophase plays a significant role during cell division as it is the final step, it is
where two daughter cells form when the cell begins to spit into two different
cells. This is important because these newly created identical cells which
function the same way as their cell they duplicated from and therefore can be
utilised to build an entire organism from singular zygotes, they can also be used
to replaced cells which have been damaged, either naturally or unnaturally. If
telophase does not happen or fails during the stage, then the cell would no
longer be able to divide and if this occurs then it would be fetal towards
humans as you would no longer be able to make new cells therefore you cannot
replace them if they
become damaged,
for instance if you
cut yourself then it
could not heal as the
skin is made up of approximately 19 million skin
cells.
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