2. What is Down Syndrome
• DS is a naturally occurring chromosomal
arrangement that has always been a part of
the human condition, being universally
present across racial, gender or
socioeconomic lines, and affecting
approximately 1 in 800 live births, although
there is considerable variation worldwide.

4. • Down syndrome usually causes varying
degrees of intellectual and physical disability
and associated medical issues.

6. • Down syndrome (DS) or Down's syndrome,
also known as trisomy 21, is a genetic
disorder caused by the presence of all or part
of a third copy of chromosome 21
• Down syndrome is the most common
chromosome abnormality in insan or human
beings

7. • Boy with Down syndrome assembling a bookcase

8. • Down syndrome (DS), also called Trisomy 21,
is a condition in which extra genetic material
causes delays in the way a child develops,
both mentally and physically.
• It affects about 1 in every 800 babies born in
the United States.

9. • The physical features and medical problems
associated with Down syndrome can vary
widely from child to child.
• While some kids with DS need a lot of medical
attention, others lead healthy lives.

10. • It is typically associated with a delay
in cognitive ability (mental retardation)
and physical growth, and a particular set of
facial characteristics
• Cognition is a group of mental processes that
includes attention, memory, producing and
understanding language, learning, reasoning,
problem solving, and decision making

12. • The average IQ of young adults with Down
syndrome is around 50, whereas young adults
without the condition typically have an IQ of
100

13. intelligence quotient, or IQ
• It is a score derived from one of
several standardized tests designed to
assess intelligence.
• The abbreviation "IQ" comes from
the German term Intelligenz-Quotient,
originally coined by psychologist William
Stern.

14. • When modern IQ tests are devised, the mean
(average) score within an age group is set to
100
• Thus, the intention is that approximately 95%
of the population scores within two Standard
Deviations (SDs) of the mean, i.e. has an IQ
between 70 and 130.

15. • Mental Retardation has historically been
defined as an IQ below 70
• A large proportion of individuals with Down
syndrome have a severe degree of intellectual
disability

16. • Down syndrome is named after John Langdon
Down, the British physician who described the
syndrome in 1866
• The condition was clinically described earlier
by Jean Etienne Dominique Esquirol in 1838
and Edouard Seguin in 1844

17. • Down syndrome was identified as a
chromosome 21 trisomy by Dr. Jérôme
Lejeune in 1959
• Down syndrome can be identified in a baby at
birth or before birth by prenatal screening
• Pregnancies with this diagnosis are
often terminated.

18. • The CDC estimates that about one of every
691 babies born in the United States each year
is born with Down syndrome
• Centers for Disease Control and
Prevention (CDC) is the national public health
institute of the United States

19. • Many children with Down syndrome are
educated in regular school classes while
others require specialized educational
facilities.
• Some children graduate from high school and,
in the US, there are increasing opportunities
for participating in post-secondary education

20. • Education and proper care has been shown to
improve quality of life significantly
• Many adults with Down Syndrome are able to
work at paid employment in the community,
while others require a more sheltered work
environment

21. • The signs and symptoms of Down syndrome
are characterized by the neotenization of the
brain and body
• In neoteny, the physiological (or somatic)
development of an organism is slowed or
delayed

22. • Down syndrome is characterized by
decelerated maturation (neoteny), incomplete
morphogenesis (vestigia) and atavisms
• Atavism is the tendency to revert to ancestral
type. In biology, an atavism is an evolutionary
throwback, such as traits reappearing which
had disappeared generations before

24. • Individuals with Down syndrome may have
some or all of the following physical
characteristics:
• microgenia (abnormally small chin)
• oblique eye fissures on the inner corner of the
eyes
• muscle hypotonia (poor muscle tone)

26. • a flat nasal bridge
• a single palmar fold
• a protruding tongue (due to small oral cavity,
and an enlarged tongue near the tonsils)
or macroglossia
• face is flat and broad
• a short neck,

28. • white spots on the iris known as Brushfield
spots
• excessive joint laxity including atlanto-
axial instability
• excessive space between large toe and second
toe

30. • a single flexion furrow of the fifth finger,
• a higher number of ulnar loop dermatoglyphs
• short fingers
• Growth parameters such as height, weight,
and head circumference are smaller in
children with DS than with typical individuals
of the same age

32. • Adults with DS tend to have short stature and
bowed legs
• average height for men is 5 feet 1 inch
(154 cm) and for women is 4 feet 9 inches
(144 cm)
• Individuals with DS are also at increased risk
for obesity as they age

33. Genetics
• Down syndrome disorders are based on
having too many copies of the genes located
on chromosome 21.
• In general, this leads to an overexpression of
the genes
• It is estimated that chromosome 21 contains
200 to 250 genes

34. What causes it
• Normally, at the time of conception a baby
inherits genetic information from its parents
in the form of 46 chromosomes:
• 23 from the mother and 23 from the father.

35. • In most cases of Down syndrome, a child gets
an extra chromosome 21 — for a total of 47
chromosomes instead of 46.
• It's this extra genetic material that causes the
physical features and developmental delays
associated with DS.

36. Trisomy 21
• Trisomy 21 (47,XX,+21) is caused by
a meiotic nondisjunction event.
• With nondisjunction, a gamete (i.e., a sperm
or egg cell) is produced with an extra copy of
chromosome 21; the gamete thus has 24
chromosomes.

38. • When combined with a normal gamete from the
other parent, the embryo now has 47
chromosomes, with three copies of chromosome
21.
• Trisomy 21 is the cause of approximately 95% of
observed Down syndromes, with 88% coming from
nondisjunction in the maternal gamete and 8%
coming from nondisjunction in the paternal gamete

39. • Although no one knows for sure why DS
occurs and there's no way to prevent the
chromosomal error that causes it, scientists do
know that women age 35 and older have a
significantly higher risk of having a child with
the condition.

40. • At age 30, for example, a woman has about a
1 in 1,000 chance of conceiving a child with
DS.
• Those odds increase to about 1 in 400 by age
35.
• By 40 the risk rises to about 1 in 100.

41. • Graph showing
probability of Down
syndrome as a
function of
maternal age.

42. • Recent research has identified a region of the
chromosome that contains the main genes
responsible for the pathogenesis of Down
syndrome
• The actual Down syndrome "critical region"
encompasses chromosome bands 21q22.1-
q22.3

43. Robertsonian translocation
• The extra chromosome 21 material that
causes Down syndrome may be due to
a Robertsonian translocation in the karyotype
of one of the parents.
• In this case, the long arm of chromosome 21 is
attached to another chromosome,
often chromosome 14
[45,XX,der(14;21)(q10;q10)].

44. • In humans, when a Robertsonian translocation
joins the long arm of chromosome 21 with the
long arm of chromosome 14 (or 15), the
heterozygous carrier is phenotypically normal
because there are two copies of all major
chromosome arms and hence two copies of all
essential genes.

46. • However, the progeny of this carrier may
inherit an unbalanced trisomy 21,
causing Down Syndrome.
• About one in a thousand newborns has a
Robertsonian translocation.

47. • A person with such a translocation is
phenotypically normal.
• During reproduction,
normal disjunctions leading to gametes have a
significant chance of creating a gamete with
an extra chromosome 21, producing a child
with Down syndrome.

49. • Translocation Down syndrome is often
referred to as familial Down syndrome.
• It is the cause of 2–3% of observed cases of
Down syndrome
• It does not show the maternal age effect, and
is just as likely to have come from fathers as
mothers

51. • Though Down syndrome can't be prevented, it
can be detected before a child is born.
• The health problems that may go along with
DS can be treated, and many resources are
available to help kids and their families who
are living with the condition.