Trisomy 21 (Down Syndrome)

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Trisomy 21(Down Syndrome)

• By Abby Foulk

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Inheritance Pattern

• Trisomy 21 is a Nondisjunction.
• -Nondisjunction An event during meiosis in
  which homologous chromosomes or sister
  chromatids fail to separate.

• An extra chromosome is located on the 21st group

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Location

• Trisomy 21 (Down Syndrome) is located on
  chromosome 21.

Extra Chromosome 21
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Trisomy 21 is not located on a gene, but possible
genes that could be affected by Trisomy 21 are
Superoxide Dismutase (SOD1) over expression may
cause premature aging and decreased function of
the immune system its role in Senile Dementia of
the Alzheimer's type or decreased cognition is
still speculative COL6A1 over expression may
be the cause of heart defects ETS2 over
expression may be the cause of skeletal
abnormalities CAF1A over expression may be
detrimental to DNA synthesis Cystathione Beta
Synthase (CBS) over expression may disrupt
metabolism and DNA repair DYRK over
expression may be the cause of mental retardation
CRYA1 over expression may be the cause of
cataracts GART over expression may disrupt
DNA synthesis and repair IFNAR -- the gene for
expression of Interferon, over expression may
interfere with the immune system as well as other
organ systems
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Who is most likely to get Trisomy 21?

• No gender is more likely to have Trisomy 21 than
  others.
• The older a woman is, the chance of her giving
  birth to a child with Trisomy 21 is greater.

Older women do have a more likely chance of
having a child with down syndrome. But because
younger women are giving birth to more babies,
the majority of babies with down syndrome come
from younger mothers.
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• At age 25, the risk of having a baby with Down
  syndrome is 1 in 1,250.
• At age 30, the risk is 1 in 1,000.
• At age 35, the risk is 1 in 400.
• At age 40, the risk is 1 in 100.
• At age 45, the risk is 1 in 30.

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Symptoms

• There are many Symptoms of Trisomy 21
• Decreased muscle tone at birth
• Excess skin at the nape of the neck
• Flattened nose
• Separated joints between the bones of the skull
• Single crease in the palm of the hand
• Small mouth
• Upward slanting eyes
• Wide, short hands with short fingers
• White spots on the colored part of the eye
• Smaller head than average
• Abnormally shaped head
• Never fully reach their average adult height

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and more Symptoms

• Usually you can tell a person has down syndrome
  by looking at them.
• Also, people with Down syndrome may have
• -impulsive behavior
• -poor judgment
• -short attention span
• -slow learning abilities
• People with Down Syndrome also have a great risk
  of having heart defects and some will even need
  to have major surgery after birth.

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How common is this Disorder?

• Trisomy 21 effects one in every eight-hundred
  babies
• (About 3,400 babies a year in the U.S.)

According to the National Down Syndrome Society,
there are more than 400,000 individuals with Down
syndrome in the United States
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Can Trisomy 21 be deadly and Does it shorten the
afflicted persons lifespan?
Trisomy 21 can be deadly.
Statistics show that

• 15 will die before turning the age of one.

• 35 will die at the age of fifty.

50 will die after turning the age of fifty.
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Diagnosis

• People can be tested for Trisomy 21, usually
  while they are still in the womb or after the
  baby is born. Some of these tests include
• Amniocentesis. A sample of the amniotic fluid
  surrounding the fetus is withdrawn through a
  needle inserted into the mother's uterus. This
  sample is then used to analyze the chromosomes of
  the fetus. Doctors usually perform this test
  after 15 weeks of gestation. The test carries a
  one in 200 risk of miscarriage
• Chorionic villus sampling (CVS). Cells taken from
  the mother's placenta can be used to analyze the
  fetal chromosomes. Typically performed between
  the ninth and 14th week of pregnancy, this test
  carries a one in 100 risk of miscarriage.
• Percutaneous umbilical blood sampling (PUBS).
  Blood is taken from a vein in the umbilical cord
  and examined for chromosomal defects. Doctors
  generally perform this test after 18 weeks of
  gestation. This test carries a greater risk of
  miscarriage than does amniocentesis or chorionic
  villus sampling. Generally, this test is only
  done when speed of diagnosis is essential.

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More Diagnosiss
After birth, the initial diagnosis of Down
syndrome is often based on the baby's appearance.
If your child displays some or all of the
characteristics of Down syndrome, your doctor
probably will order a test called a chromosomal
karyotype. This test is an analysis of your
child's chromosomes. If there's an extra
chromosome 21 present in all or some of the
cells, the diagnosis is Down syndrome.
Each of these three tests is 98 to 99 percent
accurate in diagnosing Down syndrome before
birth.
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Is there a treatment or cure (permanent fix of
symptoms) for Trisomy 21?
There is no treatment or cure for down
syndrome. However, there are some cures for heart
defects, which is a symptom of down syndrome.
Surgery is that number one fix.
Even though there are no exact treatments, people
with down syndrome can still live successful
lives.
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Are there any support groups?
NATIONAL DOWN SYNDROME SOCIETY -National Down
Syndrome Society 666 Broadway, 8th Floor New
York, New York 10012 - 800-221-4602  -  info_at_n
dss.org   
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Interesting Facts

• 92 of women who know that their fetus has
  Trisomy 21 (Down Syndrome) choose abortion.
• - Brian Skotko

• Down syndrome is really the only trisomy
  compatible with life. Only two other trisomies
  have been observed in babies born alive
  (trisomies 13 and 18), but babies born with these
  trisomies have only a 5 chance of surviving
  longer than one year.
• In 90 of Trisomy 21 cases, the additional
  chromosome comes from the mother's egg rather
  than the father's sperm.
• Down syndrome was originally described in 1866 by
  John Langdon Down. It wasn't until 1959 that a
  French doctor, named Jerome Lejeune, discovered
  it was caused by the inheritance of an extra
  chromosome 21

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More interesting facts
Sarah Palins son, Trig, has down syndrome
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Works Cited
Johnson, Summer. "Will The Down Syndrome Children
Disappear? Blog.bioethics.net."
Blog.bioethics.net a Nature Top 50 Science Blog
from The American Journal of Bioethics. Center of
Practical Bioethics, 16 Sept. 2009. Web. 25 Jan.
2011. lthttp//blog.bioethics.net/2009/09/will-th
e-down-syndrome-children-disappear/gt. Leshin,
Len. "Trisomy 21 The Origin of Down Syndrome."
Down Syndrome Health Issues - Medical Essays and
Information. 1997. Web. 25 Jan. 2011.
lthttp//www.ds-health.com/trisomy.htmgt. March
of Dimes. "Down Syndrome Baby March of
Dimes." Pregnancy, Baby, Prematurity, Birth
Defects March of Dimes. July 2009. Web. 25 Jan.
2011. lthttp//www.marchofdimes.com/Baby/birthdefec
ts_downsyndrome.html?gclidCK_QxffV1qYCFULNKgodMwp
TIAgt.
Staff, Mayo Clinic. "Down Syndrome Tests and
Diagnosis - MayoClinic.com." Mayo Clinic. 5 Nov.
2010. Web. 26 Jan. 2011. lthttp//www.mayoclinic.co
m/health/down-syndrome/DS00182/DSECTIONtests-and-
diagnosisgt.
University of Utah. "Down Syndrome."
Learn.Genetics. 2011. Web. 26 Jan. 2011.
lthttp//learn.genetics.utah.edu/content/disorders/
whataregd/down/gt.