5. It is a common
autosomal trisomy
among live –born
children ,it has
frequency of about 1 in
800 of live birth .
It doesn't usually run in
families and it
increases with the
mother age.
6. Children with this
syndrome are invariably
mentally retarded.
There is similarity
between people with
Alzheimer disease and
adults ”over 30” with
down syndrome . They
share memory loss,
confusion, anxiety ,and
lost of ability to perform
simple tasks like dressing
or feeding .
7. The physiological
symptoms
There are of small statures due
to delayed maturation of the
skeletal system and their
muscle tone is poor.
They have a characteristic
face appearance. It is broad
and flat with a small nose
,irregular teeth, abnormally
shaped ears and thick lips .
Many of them have peculiar
small fold of skin across this
inner part of the eye this gives
the eyes a slightly oriental look.
The name “mongolism” is
derived from this characteristic
8. They have large furrowed
tongue.
40%of children with the
syndrome have major heart
defects.
Defects of kidneys ,thyroid
gland and Adrenal glands are
so common with this syndrome.
Some highly usual
dermatoglyphic
(glyphic=craving) patterns of
hand creases ,fingerprints and
foot prints are also associated
with this syndrome.
9. Hipbones are abnormally shaped and the
feet's little fingers often short and curved
inward.
Males have poorly developed genitals and
Are invariably sterile,in females ovarian
defects and irregular menstruation but
fertility is possible.
Many children learn to talk but speech is
usually thick and harsh sounding ,perhaps
in part because of hearing defects.
10. This syndrome affects about
one in 4,500 Live-born
children.
Approximately 65 % of those
individuals are females ,males
with the syndrome are more
likely to undergo spontaneous
abortion.
Karyotype:(47,XX or XY+18)
means having extra 18
chromosome.
11. They have multiple
abnormalities including severe
mental and physical
retardation.
Such as :
1-elongated skull with low set
malformed ,sometimes pointed
ears ,their jaw and oral cavity is
small .
2-They carry their fingers in an
abnormal position with the
second finger overlapping the
third.
Life expectancy of males is
about 3 months ,in affected
females it is about nine months.
12. Virtually no live –born
babies having trisomy
16 are seen, cause this
trisomy is often
encountered in early
abortuses
Karyotype:
47 chromosome including
an extra chromosome
which is chromosome
number 16
13. It occurs in about one in 5,000
live births.
Affected children rarely survive
more than3-4 moths after birth .
Karyotype:
(47, XX or XY +13) Having extra
13 chromosome is the reason
for that abnormality.
Affected children are severely
retarded both mentally and
physically.
14. Small skull and eyes.
The ears are often
malformed and deafness
in common.
Many have malformed
thumbs and extra digits.
70%have heart defects.
15.
16. A chromosome abnormality that causes individuals to have an abnormal number of
chromosomes is called aneuploidy. If the zygote has an additional chromosome
(three instead of two) it is trisomic for that chromosome. If the zygote is missing a
chromosome it is monosomic. Aneuploid cells occur as a result of chromosome
breakage or nondisjunction errors that happen during meiosis. Two types of errors
occur during nondisjunction: homologous chromosomes don't separate
during anaphase I of meiosis I or sister chromatids don't separate during anaphase
II of meiosis II.
In sex chromosomes, nondisjunction results in a number of abnormalities. Klinefelter
syndrome is a disorder in which males have an extra X chromosome. The genotype
for males with this disorder is XXY. People with Klinefelter syndrome may also have
more than one extra chromosome resulting in genotypes which include XXYY,
XXXY, and XXXXY. Other mutations result in males that have an extra Y
chromosome and a genotype of XYY. These males were once thought to be taller
than average males and overly aggressive based on prison studies. Additional
studies however have found XYY males to be normal. Tuner syndrome is a condition
that affects females. Individuals with this syndrome, also called monosomy X, have
a genotype of only one X chromosome (XO). Trisomy X females have an additional
X chromosome and are also referred to as metafemales (XXX).
Nondisjunction can occur in autosomal cells as well. Down syndrome is most
commonly the result of nondisjunction affecting autosomal chromosome 21. Down
syndrome is also referred to as trisomy 21 because of the extra chromosome.
17. 45 XO, encompasses several
conditions in human females, of
which monosomy X (absence of an
entire sex chromosome, the Barr
body) is most common. It is
a chromosomal abnormality in
which all or part of one of the sex
chromosomes is absent
(unaffected humans have 46
chromosomes, of which two are
sex chromosomes). Normal females
have two X chromosomes, but in
Turner syndrome, one of those sex
chromosomes is missing or has
other abnormalities.
18. 47, XXY, or XXY syndrome is a
condition in which human males have
an extra X chromosome. While females
have an XX chromosomal makeup,
and males an XY, affected individuals
have at least two X chromosomes and
at least one Y chromosome. Because
of the extra chromosome, individuals
with the condition are usually referred
to as "XXY Males", or "47, XXY Males"
19. XYY syndrome is an aneuploidy (abnormal number) of
the sex chromosomes in which a human male receives an
extra Y-chromosome, giving a total of 47 chromosomes
instead of the more usual 46. This produces
a 47,XYY karyotype which occurs in 1 in 1000 male births.
Some medical geneticists question whether the term
"syndrome" is appropriate for this condition[ because its
clinical phenotype is norma and the vast majority (an
estimated 97% in Britain) of 47,XYY males do not know
their karyotype.
20. Triple X syndrome is a form
of chromosomal variation characterized by the
presence of an extra X chromosome in each cell of
a human female. The condition always produces
females, with an XX pair of chromosomes, as well
as an additional chromosome, resulting in the
formation of XXX.
