By: Abby Foulk
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
Location:
• Trisomy 21 (Down Syndrome) is located on chromosome 21.
Extra Chromosome
21
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
• 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.
•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.
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
• 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.
Trisomy 21 can be deadly.
Statistics show that:
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.
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.
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.
NATIONAL DOWN SYNDROME SOCIETY:
-National Down Syndrome Society
666 Broadway, 8th Floor
New York, New York 10012
- 800-221-4602
- info@ndss.org
•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
Sarah Palin’s son, Trig, has down syndrome
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.
<http://blog.bioethics.net/2009/09/will-the-down-syndrome-children-disappear/>.
Leshin, Len. "Trisomy 21: The Origin of Down Syndrome." Down Syndrome: Health Issues - Medical
Essays and Information. 1997. Web. 25 Jan. 2011.
<http://www.ds-health.com/trisomy.htm>.
March of Dimes. "Down Syndrome | Baby | March of Dimes." Pregnancy, Baby, Prematurity, Birth
Defects | March of Dimes. July 2009. Web. 25 Jan. 2011.
<http://www.marchofdimes.com/Baby/birthdefects_downsyndrome.html?gclid=CK_QxffV1qYCFUL
NKgodMwpTIA>.
Staff, Mayo Clinic. "Down Syndrome: Tests and Diagnosis - MayoClinic.com." Mayo Clinic. 5 Nov.
2010. Web. 26 Jan. 2011. <http://www.mayoclinic.com/health/downsyndrome/DS00182/DSECTION=tests-and-diagnosis>.
University of Utah. "Down Syndrome." Learn.Genetics™. 2011. Web. 26 Jan. 2011.
<http://learn.genetics.utah.edu/content/disorders/whataregd/down/>.