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Karyotypes
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A picture that displays an individual’s
chromosomes arranged in homologous pairs
and in order of diminishing size.
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Cells (from blood, amniotic fluid, etc)
are grown in vitro (in a cell culture
dish) to increase their number
Cell division is then arrested in
metaphase with colchicine (prevents
mitotic spindle from forming)
Cells are centrifuged and lysed to
release chromosomes
Chromosomes are stained,
photographed, and grouped by size
and banding patterns
This is a photograph of the 46 human
chromosomes in a somatic cell, arrested in
metphase. Can you see that they are duplicated
sister chromatids?
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Occurs when either homologues fail to separate during anaphase
I of meiosis, or sister chromatids fail to separate during anaphase
II.
The result is that one gamete has 2 copies of one chromosome
and the other has no copy of that chromosome. (The other
chromosomes are distributed normally.)
If either of these gametes unites with another during fertilization,
the result is aneuploidy (abnormal chromosome number)
A trisomic cell has one extra chromosome (2n +1) = example:
trisomy 21. (Polyploidy refers to the condition of having three
homologous chromosomes rather then two)
A monosomic cell has one missing chromosome (2n - 1) = usually
lethal except for one known in humans: Turner's syndrome
(monosomy XO).
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Symptoms
 Short stature
 Weak muscles
 Short, wide neck
 A single crease aross the palms of the hands
 Small low set ears
 Intellectual disability, mild to moderate
 Heart defects…
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Symptoms
 Shorter stature
 Webbed neck
 Do not mature sexually during puberty
 Infertile
 Normal intelligence
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Symptoms
 Normal to slightly below average intelligence
 Taller, slimmer body
 Fertile
 Usually cannot be detected unless a genetic test is
performed
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Symptoms
 Slightly taller
 Slightly lower intelligence
 Slightly out turned elbows
 Testosterone slightly higher
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Symptoms
 Serious eye, brain and circulatory defects
 Cleft palate
 Life expectancy if not still born is only a few
months
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Symptoms
 Every organ is affected
 Kidney and heart defects
 Life expectancy is only a few months