Atypical Cell Division
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Sometimes, body processes can go wrong. One
of these processes is cell division.
When something goes wrong with a somatic
cell, there are millions of other cells in the
same place so it often causes no noticeable
effect.
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When something goes wrong with a
reproductive cell, however, it is more trouble.
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If that sperm or egg with a problem results in
an embryo all of the cells will be affected.
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Nondisjunction is a failure to separate that
can occur between two homologous
chromosomes during meiosis.
As a result, one of the daughter cells is
missing a chromosome, and the other has an
extra chromosome. These cells will not
function properly.
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If the cell with the extra chromosome
develops, one of the problems is Down
syndrome.
People with Down syndrome have an extra
chromosome on pair 21. This usually results in
a mental disability, though there are a wide
range of possibilities.
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Klinefelters syndrome is another example of
too many chromosomes. The child inherits two
X chromosomes and a Y chromosome.
The child is a male, but has high levels of
estrogen. They do not develop sperm and
cannot father children.
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An example of a disorder caused by not
enough chromosomes is Turners syndrome.
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Turner syndrome occurs when a female baby
has only one X chromosome. These females do
not mature sexually and are shorter in height.
Karyotyping
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A karyotype is a picture of the chromosomes
from a cell, arranged in homologous or similar
pairs.
The chart is organized from the largest pair
(#1) to the shortest pair (#22).
Pair #23 are the sex chromosomes. Remember
that because a male has mismatched sex
chromosomes that will be the only time the
two chromosomes don’t look exactly the same.