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ABNORMALITY DUE TO CHANGES IN THE NUMBER OF CHROMOSOMES

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ABNORMALITY DUE TO CHANGES IN THE NUMBER OF
CHROMOSOMES
C
hromosom
e
s in living things
a
r
e
usu
a
lly foun
d
in p
a
irs
,
known
a
s
d
iploi
d
.
D
iploi
d c
hromosom
e
s
a
r
e
m
a
int
a
in
ed
through mitoti
c d
ivision
,
n
a
m
e
ly
ce
ll
d
ivision
pro
ce
ss
e
s th
a
t pro
d
u
ce
two
c
hil
d ce
lls th
a
t
a
r
e
i
de
nti
ca
l to st
e
m
ce
lls
.
Pa
ir
ed
c
hromosom
e
s
(
homologous
c
hromosom
e
s
)
h
a
v
e
simil
a
r sh
a
p
e
s
,
siz
e
s
a
n
d
c
ompositions
.
I
n hum
a
ns
,
e
v
e
ry som
a
ti
c ce
ll h
a
s
46
c
hromosom
e
s or
23
p
a
irs
,
e
x
ce
pt sp
e
rm
ce
lls
a
n
d
ovum th
a
t h
a
v
e a
s
e
t of
c
hromosom
e
s
.
H
um
a
n
c
hromosom
e
s
c
onsist of two s
e
ts
,
eac
h of th
e
23
c
hromosom
e
s
,
whi
c
h is
a
s
e
t of
origin
a
ting from th
e
moth
e
r
a
n
d a
s
e
t of f
a
th
e
r
.
C
hromosom
e ab
norm
a
liti
e
s
a
r
e d
ivi
ded
into two typ
e
s
,
n
a
m
e
ly
ab
norm
a
liti
e
s of th
e
num
be
r of
c
hromosom
e
s
a
n
d c
hromosom
e
stru
c
tur
a
l
ab
norm
a
liti
e
s
.
I
n norm
a
l
hum
a
ns
,
th
e
num
be
r of
c
hromosom
e
s is
46
(
d
iploi
d
).
T
h
e
num
be
r of
c
hromosom
e
s
ca
n
be a
n
e
uploi
d
i or polyploi
d
y
.
E
uploi
d
i r
e
f
e
rs to v
a
ri
a
tions involving
a
ll
c
hromosom
e
s
e
ts
,
whil
e a
n
e
uploi
d
i r
e
f
e
rs to v
a
ri
a
tions th
a
t only involv
e
singl
e
c
hromosom
e
s in
a c
hromosom
e
s
e
t
.
a
.
E
uploi
d
i
I
n
d
ivi
d
u
a
l
e
uploi
d
i h
a
s
a c
ompl
e
t
e c
hromosom
e
s
e
t
.
Tab
l
e
1
.
Va
ri
a
tions r
e
g
a
r
d
ing th
e c
ompl
e
t
e
s
e
t of
c
hromosom
e
s
E
uploi
d
i typ
e
N
um
be
r of g
e
nom
e
s
R
omosom
ed c
ompl
e
m
e
nt
M
onoploi
d
i
O
n
e
(
N
)
A B C
d
iploi
d
i
two
(
2
n
)
Aabbcc
P
loliploi
d
i
mor
e
th
a
n
2
N
triploi
d
i
T
hr
ee
(
3
n
)
Aaabbbccc
t
e
tr
a
ploi
d
i
F
our
(
4
n
)
Aaaabbbbcccc
p
e
nt
a
ploi
d
i
F
iv
e
(
5
N
)
Aaaaabbbbbccccc
h
e
ks
a
ploi
d
i
S
ix
(
6
N
)
s
e
pt
a
ploi
d
i
Se
v
e
n
(
7
n
)
oktoploi
d
i
E
ight
(
8
n
)
He
r
e a
r
e
th
e
p
a
r
a
phr
a
s
e
s of th
e
t
e
xt you provi
ded
:
b
r
ea
kf
a
st
.
M
onoploi
d
i
M
onopl
e
oi
d
i is r
a
r
e
ly foun
d
in
a
nim
a
ls
,
e
x
ce
pt for m
a
l
e
hon
e
y
bee
s th
a
t o
cc
ur
through p
a
rtth
e
nog
e
n
e
sis
.
H
ow
e
v
e
r
,
monoploi
d
i is oft
e
n foun
d
in pl
a
nts su
c
h
a
s
a
lg
ae
,
fungus
,
a
n
d
moss
.
I
n
d
ivi
d
u
a
l monoploi
d
i usu
a
lly shows
ab
norm
a
l growth
a
n
d
r
a
r
e
ly r
eac
h
e
s th
e ad
ult st
a
g
e
.
C
..
P
oliploi
d
i
I
n
d
ivi
d
u
a
ls with thr
ee
or mor
e c
ompl
e
t
e c
hromosom
e
s
e
ts
a
r
e ca
ll
ed
polyploi
d
i
.
T
his
c
on
d
ition is
c
ommon in pl
a
nts
b
ut v
e
ry r
a
r
e
ly in
a
nim
a
ls
.
Te
tr
a
ploi
d
i
(
4
N
)
pl
a
nts
pro
d
u
ce
2
n g
a
m
e
t
e
s
,
whi
c
h in m
a
ny sp
ec
i
e
s
ca
n f
e
rtiliz
e
th
e
ms
e
lv
e
s
,
pro
d
u
ce
m
a
ny
t
e
tr
a
ploi
d
i pl
a
nts
.
Ab
out two
-
thir
d
s of gr
a
ss sp
ec
i
e
s
a
r
e e
stim
a
t
ed
to
be
polyploi
d
i
.
P
oliploi
d
i pl
a
nts h
a
v
e ad
v
a
nt
a
g
e
s su
c
h
a
s
a b
ro
ade
r
d
istri
b
ution
,
th
e ab
ility to
c
oloniz
e
in n
e
w
a
r
ea
s
,
a
n
d
r
e
sist
a
n
ce
to
d
iff
e
r
e
nt h
ab
it
a
ts th
a
n
d
iploi
d
pl
a
nts
.
T
h
e
y
a
lso h
a
v
e
f
e
w
e
r stom
a
t
a
in
d
i
ce
s
b
ut l
a
rg
e
r stom
a
t
a
siz
e
.
I
n
a
nim
a
ls
,
polyploi
d
i oft
e
n
ca
us
e
s im
ba
l
a
n
ce
s in
de
t
e
rmining g
e
n
de
r
,
whi
c
h
ca
n l
ead
to st
e
riliz
a
tion
.
I
n hum
a
ns
,
polyph
a
nsi
a
r
e
not foun
d
;
known
ca
s
e
s usu
a
lly r
e
sult in spont
a
n
e
ous mis
ca
rri
a
g
e
or
dea
th
,
a
n
d
if foun
d
,
only l
a
st
a
f
e
w hours
.
d
.
A
n
e
uploi
d
i
A
n
e
uploi
d
i is
a c
hromosom
e ab
norm
a
lity th
a
t oft
e
n o
cc
urs in n
e
w
b
orns
a
n
d
is oft
e
n
r
e
l
a
t
ed
to g
e
st
a
tion
a
l
a
g
e
,
a
n
d
is
a c
ommon
ca
us
e
of spont
a
n
e
ous
ab
ortion
ca
us
ed
b
y
c
hromosom
e ab
norm
a
liti
e
s
.
A
n
e
uploi
d
i
ca
n
be de
t
ec
t
ed be
for
e b
irth
.
I
n
d
ivi
d
u
a
ls
with
a
n
e
uploi
d
i h
a
v
e a
num
be
r of
c
hromosom
e
s th
a
t
a
r
e
l
e
ss or mor
e
th
a
n th
e
num
be
r of
d
iploi
d
norm
a
l
c
hromosom
e
s
(
e
g
2
n
-
1
,
2
n
-
2
,
2
n
+
1
,
2
n
+
2
).
B
ri
d
g
e
s
'
s
d
is
c
ov
e
ry in
1916
c
on
ce
rning
D
rosophil
a
fli
e
s with
a
short
a
g
e
of
c
hromosom
e
s
-
x
(
Ma
l
e XO
)
a
n
d
th
e e
x
ce
ss g
e
nit
a
l
c
hromosom
e
(
XXY
)
ca
us
ed b
y non
d
isjun
c
tion
d
uring g
a
m
e
tog
e
n
e
sis
.
I
n th
e
hum
a
n popul
a
tion
,
a
n
e
uploi
d
i is g
e
n
e
r
a
lly
ca
us
ed b
y
non
d
isjun
c
tion
d
uring th
e
form
a
tion of g
a
m
e
t
.
Tab
l
e
2
.
Va
ri
a
tions in
a
n
e
uploi
d
i
T
yp
e
N
um
be
r of
c
hromosom
e
s
E
x
a
mpl
e
D
is
c
om
(
norm
a
l
)
2
n
Aa bb cc
M
onosomi
2
n
-
1
Aa bb c
N
ullisomi
2
n
-
2
Aa bb c
P
oli
c
yomy
:
e
xtr
a c
hromosom
e
a
.
T
risomy
2
n
+
1
AA BB CCC
b
r
ea
kf
a
st
.
D
o
be
l
T
risomy
2
n
+
1
+
1
AA BBB CCC
C
..
t
e
tr
a
somi
2
n
+
2
AA BB CCCC
d
.
p
e
nt
a
somi
2
n
+
3
Aa bb ccccc
He
y
.
h
e
ks
a
somi
2
n
+
4
Aa bb H
ot
e
ls
f
.
s
e
pt
a
somi
2
n
+
5
st
a
rs
AA BB CCCCCCC
Tab
l
e
3
.
A
n
e
uploi
d
i in th
e
hum
a
n popul
a
tion
beca
us
e
of non
d
i
S
ju
c
tion
C
hromosom
e
nom
e
n
c
l
a
tur
e
C
hromosom
e
formul
a
C
lini
c
syn
d
rom
e
45
,
x
2
n
-
1
T
urn
e
r
47
, +
21
2
n
+
1
D
own
47
, +
13
2
n
+
1
T
risomy
13
47
, +
18
2
n
+
1
T
risomy
18
47
,
xxy
2
n
+
1
K
lin
e
f
e
lt
e
r
48
,
xxxy
2
n
+
2
48
,
xxyy
2
n
+
2
49
,
xxxxy
2
n
+
3
50
,
xxxxxx
2
n
+
4
47
,
XXX
2
n
+
1
T
ripl
e
-
x
M
onosomy in hum
a
ns
a
.
T
urn
e
r
S
yn
d
rom
e
(
45
,
XO
or
44
A
+
X
)
I
n
1938
,
T
urn
e
r foun
d a
wom
a
n with
a
norm
a
l look
,
b
ut
a
ft
e
r furth
e
r
e
x
a
min
a
tion
,
foun
d
v
a
rious
ab
norm
a
liti
e
s su
c
h
a
s
a
short
b
o
d
y
(
only
120
c
m in
ad
ulthoo
d
),
th
e ab
s
e
n
ce
of ov
a
ri
e
s
,
short n
ec
ks with th
e ba
s
e
of th
e
wings
,
wi
de
c
h
e
st
,
a
n
d
s
ec
on
da
ry g
e
nit
a
lp
a
pts whi
c
h
d
o
e
s not
de
v
e
lop lik
e a b
r
ea
st
a
n
d
pu
b
i
c
h
a
ir th
a
t
d
o
e
sn
'
t grow
.
T
h
e
n
ec
k skin looks v
e
ry s
a
gging
.
I
t is
e
stim
a
t
ed
th
a
t on
e
in
2000
to
2500
wom
e
n
b
orn worl
d
wi
de e
xp
e
ri
e
n
ced T
urn
e
r syn
d
rom
e
.
Ab
out
15
%
of
ca
s
e
s of spont
a
n
e
ous
ab
ortion h
a
v
e Ka
ryotyp
e
45
,
X
.
Ma
ny
ca
s
e
s of
T
urn
e
r
S
yn
d
rom
e a
r
e
not
d
i
a
gnos
ed
until th
e
y
a
r
e
12
-
14
y
ea
rs
beca
us
e
th
e
y
d
o not
de
v
e
lop
s
ec
on
da
ry g
e
nit
a
ls
.
T
urn
e
r
S
yn
d
rom
e ca
n
be
r
ec
ogniz
ed
sin
ce
th
e bab
y with
add
ition
a
l skin on th
e
n
ec
k
,
a
n
d
th
e
s
e
x
c
hrom
a
tin t
e
st shows n
e
g
a
tiv
e
r
e
sults
.
Pa
ti
e
nts h
a
v
e
k
a
ryotyp
e
s
45
,
x
a
n
d
th
e
ir ov
a
ri
e
s only show th
e
r
e
st of th
e
n
e
twork
,
so th
e
y
a
r
e
st
e
ril
e
.
Ma
king
k
a
riotyp
e
s show only on
e c
hromosom
e
-
X
,
so th
e
p
a
ti
e
nt h
a
s
45
c
hromosom
e
s
,
whil
e
norm
a
l wom
e
n h
a
v
e
46
c
hromosom
e
s with two
c
hromosom
e
s
-
x
(
xx
).
T
urn
e
r syn
d
rom
e
m
a
y
be ca
us
ed b
y non
d
isjun
c
tion wh
e
n th
e
form
a
tion of
a
n
e
gg
b
y th
e
moth
e
r or th
e
loss of g
e
nit
a
l
c
hromosom
e
s
d
uring mitosis
a
ft
e
r th
e
form
a
tion
of
Z
igot
e XX
or
XY
.
T
his possi
b
ility is support
ed b
y th
e
high fr
e
qu
e
n
c
y of
M
os
a
i
c
whi
c
h
a
pp
ea
rs
a
ft
e
r th
e
form
a
tion of zygot in th
e
p
a
ti
e
nt
'
s
T
urn
e
r syn
d
rom
e
.
T
risomy for s
e
x g
e
n
de
r
c
hromosom
e
a
.
K
linf
e
lt
e
r
S
yn
d
rom
e
(
47
,
XXY
or
47
A
+
XXY
)
I
n
1942
,
K
linf
e
lt
e
r foun
d
in
d
ivi
d
u
a
l m
e
n with f
e
minin
e c
h
a
r
ac
t
e
risti
c
s su
c
h
a
s
e
nl
a
rg
ed b
r
ea
sts
,
l
ac
k of h
a
ir growth
,
high
b
o
d
y with long
a
rms
a
n
d
l
e
gs
,
high
soun
d
s
,
wi
de c
h
e
st
,
wi
de
hip
,
b
o
d
y h
a
ir th
a
t
d
i
d
not grow
,
a
n
d
sm
a
ll t
e
sti
c
l
e
s
a
n
d
ba
rr
e
n
.
E
xt
e
rn
a
l g
e
nit
a
l tools look norm
a
l
,
b
ut sp
e
rm
a
tozo
a
is usu
a
lly not form
ed
.
Ka
riotyp
e
shows
2
c
hromosom
e
s
-
x
a
n
d
1
c
hromosom
e
-
y
,
so th
a
t
a
tot
a
l of
47
c
hromosom
e
s
(
47
,
xxy
).
Pa
ti
e
nts
a
lso h
a
v
e
44
a
utosom
e
s
a
n
d
3
g
e
nit
a
l
c
hromosom
e
s
(
XXY
),
a
n
d c
hrom
a
tin t
e
sts show positiv
e
r
e
sults for
c
hrom
a
tin s
e
x
.
Pa
ti
e
nts g
e
n
e
r
a
lly
e
xp
e
ri
e
n
ce
m
e
nt
a
l
d
isor
de
rs
.
I
n
d
ivi
d
u
a
ls with klin
e
f
e
lt
e
r syn
d
rom
e ca
n
be
form
ed
through th
e
f
e
rtiliz
a
tion of
XX
e
ggs
b
y sp
e
rm
a
tozo
a
y or through x
-
ce
ll f
e
rtiliz
a
tion
b
y xy sp
e
rm
a
tozo
a
.
M
or
e
c
ompl
e
x k
a
ryotyp
e
s r
e
l
a
t
ed
to
K
linf
e
lt
e
r syn
d
rom
e
in
c
lu
de
xxyy
,
xxxy
,
xxxy
,
xxxxy
,
xxxxy
,
a
n
d
xxxxxy
.
A
lthough most suff
e
r
e
rs w
e
r
e b
orn of th
e
moth
e
r un
de
r th
e a
g
e
of
30
,
th
e N
on
d
isjun
c
tion of
C
hromosomo
-
X
on
a
ging oo
c
yt
e
s w
a
s mor
e
rol
e
th
a
n
N
on
d
isjun
c
tion
XY d
uring sp
e
rm
a
tog
e
n
e
sis
.
Ab
out
70
%
of
XXY
m
e
n h
a
v
e b
oth
c
hromosom
e
s of
X
from th
e
ir moth
e
rs
,
whil
e
th
e
oth
e
r
30
%
acce
pt
XY
c
hromosom
e
s from th
e
ir f
a
th
e
r
.
b
r
ea
kf
a
st
.
T
ripl
e
-
X S
yn
d
rom
e
(
47
,
XXX
or
47
A
+
XXX
)
I
n
1959
,
th
e
first
ca
s
e
of
T
ripl
e
-
X
syn
d
rom
e
w
a
s r
e
port
ed
with
Ka
ryotyp
e
47
,
XXX
.
T
h
e
s
e
in
d
ivi
d
u
a
ls h
a
v
e
f
e
m
a
l
e
ph
e
notyp
e
s
,
b
ut
a
t th
e a
g
e
of
22
,
th
e
out
e
r g
e
nit
a
ls
a
r
e
still r
e
s
e
m
b
l
ed b
y
bab
i
e
s
,
a
n
d
th
e
g
e
nit
a
ls in
a
n
d
th
e b
r
ea
sts
d
o not
de
v
e
lop
,
acc
omp
a
ni
ed b
y light m
e
nt
a
l
d
isor
de
rs
.
T
h
e
fr
e
qu
e
n
c
y of wom
e
n with
T
ripl
e
-
X
syn
d
rom
e
is
e
stim
a
t
ed
to
be be
tw
ee
n
1
in
1000
to
1
of th
e
2000
b
irths
.
T
ripl
e
-
X
syn
d
rom
e
is
c
omp
a
r
ed
with sup
e
r
d
rosophil
a
f
e
m
a
l
e
fli
e
s
(
XXX
).
H
ow
e
v
e
r
,
D
rosophil
a
fli
e
s with this
c
on
d
ition usu
a
lly
e
xp
e
ri
e
n
ce
signifi
ca
nt
ab
norm
a
liti
e
s
a
n
d
oft
e
n st
e
ril
e
or
e
v
e
n l
e
t
a
l
.
C
onv
e
rs
e
ly
,
wom
e
n with tripl
ed
-
X
syn
d
rom
e a
r
e
som
e
tim
e
s
d
iffi
c
ult to
d
istinguish from norm
a
l wom
e
n
,
e
v
e
n though
th
e
y m
a
y show symptoms su
c
h
a
s m
e
nt
a
l
d
isor
de
rs
a
n
d
v
e
ry irr
e
gul
a
r m
e
nstru
a
l
.
Jac
o
b
s r
e
s
ea
r
c
h on
a
37
-
y
ea
r
-
ol
d
wom
a
n p
a
ti
e
nt shows v
e
ry irr
e
gul
a
r m
e
nstru
a
tion
,
ov
a
ri
e
s simil
a
r to m
e
nop
a
us
a
l
c
on
d
itions
,
a
n
d ab
norm
a
liti
e
s in th
e
form
a
tion of
ov
a
ri
a
n folli
c
l
e
s
.
O
f th
e
63
ce
lls
e
x
a
min
ed
,
51
of th
e
m h
a
v
e
47
c
hromosom
e
s
,
with
add
ition
a
l
c
hromosom
e
s in th
e
form of
c
hromosom
e
-
x
.
Se
x
c
hrom
a
tin t
e
sts in
d
i
ca
t
e
th
a
t p
a
ti
e
nts h
a
v
e
two
c
hrom
a
tin s
e
x
.
I
n
add
ition
,
th
e ca
s
e
of poly
-
X
wom
e
n w
a
s
a
lso foun
d
,
in th
e
form of
Te
tr
a
-
X
(
48
,
xxxx
)
a
n
d Pe
nt
a
-
X
(
49
,
xxxxx
),
wh
e
r
e
mor
e
c
hromosom
e
-
X
,
th
e
low
e
r th
e
l
e
v
e
l of its int
e
llig
e
n
ce a
n
d
th
e
wors
e
m
e
nt
a
l
d
isor
de
rs
.
Jac
o
b
s r
e
s
ea
r
c
h shows th
a
t tripl
e
-
x wom
e
n
a
r
e
oft
e
n
ca
us
ed b
y
non
d
isjun
c
tion wh
e
n forming g
a
m
e
t
b
y moth
e
r
.
Jac
o
b
or
X
yy m
e
n
'
s syn
d
rom
e
(
47
,
xyy or
47
A
+
xyy
)
w
a
s foun
d b
y
Jac
o
b
s in s
e
v
e
n
m
e
n who h
ad e
xtr
e
m
e b
o
d
y h
e
ight
(
on
a
v
e
r
a
g
e
183
c
m
)
a
n
d IQ be
tw
ee
n
80
-
118
.
T
h
e c
hromosom
e e
x
a
min
a
tion r
e
v
ea
ls th
e e
x
ce
ss
c
hromosom
e
-
y
,
so th
e
c
hromosom
e
formul
a
is
47
,
xyy
.
S
om
e
of th
e
s
e
m
e
n show
ab
norm
a
liti
e
s in outsi
de
a
n
d dee
p g
e
nit
a
li
a
tools
,
b
ut
d
o not
ca
us
e b
o
d
y
ab
norm
a
liti
e
s
.
F
urth
e
r stu
d
i
e
s show
th
a
t
XYY
m
e
n
a
r
e
g
e
n
e
r
a
lly mor
e a
ggr
e
ssiv
e
th
a
n norm
a
l m
e
n
,
t
e
n
d
to
be
h
a
v
e
bad
ly
,
a
n
d
viol
a
t
e
th
e
l
a
w
.
T
h
e e
xist
e
n
ce
of two
c
hromosom
e
s
-
y in
X
yy m
e
n w
a
s
ca
us
ed b
y non
d
isjun
c
tion wh
e
n th
e
form
a
tion of sp
e
rm
a
tozo
a b
y f
a
th
e
r
,
with th
e
non
d
ojun
c
tion th
a
t o
cc
urr
ed d
uring
Ma
yiosis
II
pro
d
u
ced
sp
e
rm
a
tozo
a
with two
c
hromosom
e
s
.
I
f this sp
e
rm
a
tozo
a
f
e
rtiliz
e
s th
e e
gg
,
zigot
e
will
be
form
ed
to
be a
b
oy
.
FRAGIL X
syn
d
rom
e
,
a
lso known
a
s th
e Ma
rtin
Be
ll syn
d
rom
e
,
in
d
i
ca
t
e
s th
e
fr
a
gil
sit
e a
t th
e e
n
d
of th
e X c
hromosom
e a
rm
a
n
d
is lik
e
ly to
be
r
ed
u
ced b
y x
-
link
ed
.
S
ymptoms th
a
t
a
r
e
oft
e
n s
ee
n in
c
lu
de e
long
a
t
ed
f
ace
s
,
wi
de
for
e
h
ead
,
thi
c
k lips
,
l
a
rg
e
t
e
st
e
s
,
m
e
nt
a
l r
e
t
a
r
da
tion
,
b
ig
ea
rs
a
n
d
promin
e
nt
,
a
n
d ab
norm
a
l joint
fl
e
xi
b
ility
.
F
r
a
gil
X
syn
d
rom
e
is th
e
s
ec
on
d
most
c
ommon
ca
us
e
of m
e
nt
a
l
r
e
t
a
r
da
tion
a
ft
e
r
d
own syn
d
rom
e
,
g
e
n
e
r
a
lly suff
e
r
ed b
y
b
oys
,
a
n
d
inh
e
rit
ed b
y
p
a
r
e
nts who h
a
v
e
g
e
n
e
ti
c d
isor
de
rs
.
T
risomy for
A
utosom
I
n
d
ivi
d
u
a
ls
ca
n h
a
v
e a
n
ad
v
a
nt
a
g
e
of on
e a
utosom
e c
omp
a
r
ed
to norm
a
l
d
iploi
d c
on
d
itions
,
a
n
d beca
us
e
this
d
isor
de
r o
cc
urs in
a
utosom
e
s
,
b
oth m
e
n
a
n
d
wom
e
n
ca
n
e
xp
e
ri
e
n
ce
th
e
s
e c
on
d
itions
.
a
.
D
own
S
yn
d
rom
e
T
his
d
isor
de
r w
a
s first r
ec
or
ded b
y
Se
guin in
1844
,
b
ut th
e
n
e
w
c
lini
ca
l signs w
e
r
e
de
s
c
ri
bed
in
1866
b
y th
e B
ritish
d
o
c
tor
,
J
.
La
ng
d
on
D
own
.
I
niti
a
lly
,
this
c
on
d
ition
w
a
s
ca
ll
ed M
ongolism
beca
us
e
of ph
e
notypi
ca
l symptoms su
c
h
a
s m
e
nt
a
l
r
e
t
a
r
da
tion
a
n
d
fol
d
s on
e
y
e
li
d
s
.
H
ow
e
v
e
r
,
to
a
voi
d
th
e
t
e
rms th
a
t
a
r
e
off
e
nsiv
e
,
th
e
n
a
m
e
is
c
onv
e
rt
ed
into
D
own
S
yn
d
rom
e
.
Ka
ryotyp
e
shows th
e e
x
ce
ss of on
e
a
utosom num
be
r
21
.
Beca
us
e
of this
ab
norm
a
lity in
a
utosom
e
s
,
b
oth m
e
n
a
n
d
wom
e
n
ca
n
e
xp
e
ri
e
n
ce
it
,
with
c
hromosom
e
formul
a
s
47
,
XY
, +
21
for m
e
n
a
n
d
47
,
xx
, +
21
for wom
e
n
.
E
x
ce
ss
a
utosom num
be
r
21
st
a
t
ed
with
+
21
.
S
uff
e
r
e
rs of
D
own syn
d
rom
e
g
e
n
e
r
a
lly h
a
v
e a
short
e
r
b
o
d
y with som
e
tim
e
s
c
rook
ed
lim
b
s
,
h
ead
wi
d
th
,
roun
d
f
ace
,
mouth oft
e
n op
e
n
,
b
ig tongu
e
,
wi
de a
n
d
fl
a
t nos
e
,
a
n
d
th
e d
ist
a
n
ce be
tw
ee
n
e
y
e
wi
de
.
E
y
e
li
d
s h
a
v
e e
pi
ca
nti
c
fol
d
s
a
n
d
iris
e
y
e
s m
a
y
h
a
v
e
spots
"
b
rushfi
e
l
d
."
Ha
n
d
s
a
n
d
f
ee
t of th
e
un
de
rlying syn
d
rom
e
looks wi
d
th
a
n
d b
lunt
,
with th
e
p
a
lm of
th
e
h
a
n
d
oft
e
n shows
ab
norm
a
l h
a
n
d
lin
e
s
,
su
c
h
a
s only on
e
horizont
a
l lin
e
.
T
h
e
s
ec
on
d
thum
b a
n
d
fing
e
r m
a
y not m
ee
t
.
T
his
c
on
d
ition
a
lso oft
e
n
ca
us
e
s
bad
s
e
lf
hygi
e
n
e
,
low
IQ
(
be
tw
ee
n
25
-
75
,
oft
e
n l
e
ss th
a
n
40
),
a
s w
e
ll
a
s th
e
risk of h
ea
rt
d
isor
de
r
a
n
d
is sus
ce
pti
b
l
e
to
d
is
ea
s
e
.
E
v
e
n though th
e
lif
e e
xp
ec
t
a
n
c
y of th
e
suff
e
r
e
rs of
D
own syn
d
rom
e
is
ab
out
20
y
ea
rs
,
ca
n now
be
long
e
r
.
S
uff
e
r
e
rs of
D
own syn
d
rom
e
g
e
n
e
r
a
lly look h
a
ppy
a
n
d
un
a
w
a
r
e
of th
e
ir n
a
tur
a
l
de
f
ec
ts
.
Me
n
'
s suff
e
r
e
rs
a
r
e
oft
e
n st
e
ril
e
,
a
lthough th
e
r
e a
r
e ca
s
e
s wh
e
r
e
th
e
y show s
e
xu
a
l
a
w
a
r
e
n
e
ss
.
Mea
nwhil
e
,
som
e
wom
e
n with
D
own syn
d
rom
e a
r
e
known to giv
e b
irth
to
c
hil
d
r
e
n
.
I
n t
e
rms of
c
ytology
,
D
own syn
d
rom
e ca
n
be d
ivi
ded
into two typ
e
s
:
1
.
D
own
T
riplo
21
or
T
risomy
21
syn
d
rom
e
,
wh
e
r
e
suff
e
r
e
rs h
a
v
e
47
c
hromosom
e
s
(
47
,
xy
, +
21
for m
e
n
a
n
d
47
,
xx
, +
21
for wom
e
n
).
Ab
out
92
.
5
%
of th
e D
own
S
yn
d
rom
e ca
s
e
in
c
lu
ded
this typ
e
.
2
.
S
yn
d
rom
e d
own tr
a
nslo
ca
tion
,
wh
e
r
e
th
e a
utosom num
be
r
21
l
e
ngth is
a
tt
ac
h
ed
to oth
e
r
a
utosom
e
s
,
usu
a
lly
a
utosom num
be
r
14
,
a
lthough som
e
tim
e
s
a
utosom
num
be
r
15
.
S
om
e ca
s
e
s
d
own tr
a
nslo
ca
tion syn
d
rom
e ca
n
be de
riv
ed
from p
a
r
e
nts
to
c
hil
d
r
e
n
.
M
os
a
i
c
s
a
r
e
th
e
most r
a
r
e
typ
e
s
,
wh
e
r
e
only som
e ce
lls h
a
v
e
th
e ad
v
a
nt
a
g
e
s of
c
hromosom
e
21
(
T
risomy
21
).
Bab
i
e
s with
D
own
M
os
a
i
c
syn
d
rom
e
usu
a
lly h
a
v
e
symptoms
a
n
d
h
ea
lth pro
b
l
e
ms th
a
t
a
r
e
light
e
r th
a
n
bab
i
e
s who h
a
v
e
trisomy
21
c
l
a
ssi
c
s or tr
a
nslo
ca
tion
.
Ab
out
2
-
4
%
of th
e d
own syn
d
rom
e ca
s
e
is
a
typ
e
of
mos
a
i
c
.
C
hromosom
e
21
tr
a
nslo
ca
tion is
e
xpr
e
ss
ed b
y
T
(
14
Q
21
Q
),
showing th
e
tr
a
nslo
ca
tion
be
tw
ee
n th
e a
utosom long
a
rm
14
a
n
d
21
.
S
hort
-
sl
ee
v
ed c
hromosom
e
s
a
r
e
giv
e
n
th
e
l
e
tt
e
r p
.
T
h
e b
irth of
a c
hil
d
with
D
own syn
d
rom
e
is oft
e
n
a
sso
c
i
a
t
ed
with m
a
t
e
rn
a
l
a
g
e
,
whil
e
no
c
orr
e
l
a
tion is
c
onsist
e
nt with th
e a
g
e
of f
a
th
e
r
.
W
om
e
n
a
r
e b
orn with
a
ll
th
e
oo
c
yt
e
s th
a
t h
a
v
e bee
n form
ed
,
a
roun
d
s
e
v
e
n million
,
whi
c
h
a
r
e
in th
e
ph
a
s
e
of
th
e I
iosis
P
rof
a
s
e
of
P
rof
a
s
e
from
be
for
e be
ing
b
orn to ovul
a
tion
.
T
his oo
c
yt
e ca
n
e
xp
e
ri
e
n
ce
non
d
isjun
c
tion
d
uring th
a
t tim
e
.
D
own syn
d
rom
e
usu
a
lly o
cc
urs in
c
hil
d
r
e
n
b
orn to ol
de
r moth
e
rs
.
I
n
T
risomy
-
21
,
N
on
d
isjun
c
tion in
Me
iosis
I
pro
d
u
ced
a
n ovum with two
a
utosom
e
s num
be
r
21
,
a
n
d
if f
e
rtiliz
ed b
y norm
a
l sp
e
rm
a
tozo
a
,
Z
igot
T
risomy
-
21
w
a
s form
ed
.
N
on
d
isjun
c
tion
ca
n
be
influ
e
n
ced b
y f
ac
tors su
c
h
a
s
vir
a
l inf
ec
tions
,
r
ad
i
a
tion
,
a
ging
e
ggs
,
thyroi
d
fun
c
tion
d
isor
de
rs
,
a
n
d
m
a
t
e
rn
a
l
a
g
e
.
W
om
e
n ov
e
r
35
y
ea
rs
a
r
e
mor
e a
t risk of giving
b
irth to
bab
i
e
s with
D
own
syn
d
rom
e
th
a
n young
e
r wom
e
n
.
b
r
ea
kf
a
st
.
T
risom
a
-
13
syn
d
rom
e
(
Pa
t
a
u syn
d
rom
e
) (
47
a
, +
13
)
T
his syn
d
rom
e
w
a
s first
de
s
c
ri
bed b
y
Pa
t
a
u in
1960
a
n
d
r
a
r
e
ly foun
d
in
c
hil
d
r
e
n
,
n
e
v
e
r
e
v
e
n in
ad
ults
,
beca
us
e
this s
e
v
e
r
e de
f
ec
t oft
e
n r
e
sult
ed
in
dea
th in th
e
first
thr
ee
months
a
ft
e
r
b
irth
.
Pa
ti
e
nts
e
xp
e
ri
e
n
ce
m
e
nt
a
l
d
isor
de
rs
,
dea
fn
e
ss
,
lip g
a
ps
a
n
d
/
or p
a
l
a
t
e
,
polyi
dac
tions
,
sm
a
ll
e
y
e
s
,
a
n
d ab
norm
a
liti
e
s in th
e b
r
a
in
,
h
ea
rt
,
ki
d
n
e
ys
,
a
n
d
int
e
stin
e
.
Ha
n
d
s
a
n
d
f
ee
t
a
lso look
da
m
a
g
ed
.
T
his syn
d
rom
e
is
ca
us
ed
b
y non
d
i
S
ju
c
tion
.
T
risomy
-
18
syn
d
rom
e
,
a
lso known
a
s
Ed
w
a
r
d
s syn
d
rom
e
,
w
a
s first
e
xpl
a
in
ed b
y
Ed
w
a
r
d
s in
1960
.
Pa
ti
e
nts
e
xp
e
ri
e
n
ced
v
a
rious
ab
norm
a
liti
e
s su
c
h
a
s low
ea
rs
,
low
e
r j
a
ws th
a
t w
e
r
e a
lso low
,
sm
a
ll mouth
,
m
e
nt
a
l
d
isor
de
rs
,
d
ou
b
l
e
ki
d
n
e
ys
a
n
d
b
on
e
s
A
short
c
h
e
st
.
M
ost suff
e
r
e
rs
(
90
%
)
d
i
ed
in th
e
first six months
a
ft
e
r
b
irth
,
so
this syn
d
rom
e
w
a
s r
a
r
e
ly foun
d
in
ad
ult
c
hil
d
r
e
n
.
3
DE
l
e
si is losing som
e c
hromosom
e
s
d
u
e
to th
e b
rok
e
n
c
hromosom
e
.
C
hromosom
e
pi
ece
s th
a
t
d
o not h
a
v
e a ce
ntrom
a
ir
(
a
s
ce
ntri
c
)
a
r
e
l
e
ft
be
hin
d
in
A
n
a
ph
a
s
e a
n
d
de
stroy
ed
in pl
a
sm
a
.
De
l
e
si t
e
rmin
a
l o
cc
urs wh
e
n
b
rok
e
n
c
hromosom
e
s n
ea
r th
e
tip
,
whil
e
int
e
r
c
l
a
ry
de
l
e
tions o
cc
ur if
b
rok
e
n o
cc
ur in two pl
ace
s th
a
t r
e
mov
e
th
e
s
e
gm
e
nt in th
e ce
nt
e
r of th
e c
hromosom
e
.
I
f th
e de
fi
c
i
e
n
c
y in
c
lu
de
s too m
a
ny
g
e
n
e
s
,
it is usu
a
lly f
a
t
a
l or
ca
us
e
s
dea
th in th
e
wom
b
or
a
t
b
irth
.
H
ow
e
v
e
r
,
som
e
bab
i
e
s with sm
a
ll
de
fi
c
i
e
n
c
y on
c
hromosom
e
s m
a
y liv
e
long
e
r
.
4
S
in
d
rom
c
ri
-
d
u
-
c
h
a
t
,
foun
d
in
F
r
a
n
ce b
y
Le
j
e
un
e a
n
d
his
c
oll
ea
gu
e
s in
1963
,
w
a
s
n
a
m
ed
so
beca
us
e
of
a bab
y
'
s
c
rying
-
lik
e c
ry
.
O
th
e
r symptoms in
c
lu
de
sm
a
ll h
ead
s
,
wi
de
f
ace
s
,
nos
e
s su
c
h
a
s s
add
l
e
s
,
f
a
r
a
p
a
rt
,
e
y
e
li
d
s with
e
pik
a
nti
c
fol
d
s
,
m
e
nt
a
l
d
isor
de
rs
,
a
n
d
low
IQ
.
Pa
ti
e
nts usu
a
lly
d
i
e a
t th
e a
g
e
of
bab
i
e
s or
c
hil
d
r
e
n
.
Ka
riotyp
e Pa
ti
e
nts show
ed
th
e
pr
e
s
e
n
ce
of
de
l
e
tions on th
e a
utosom
a
l short
a
rm
num
be
r
5
.
T
his syn
d
rom
e ca
n o
cc
ur in wom
e
n
(
46
,
xx
,
5
p
-)
a
n
d
m
e
n
(
46
,
xy
,
5
p
-),
b
ut th
e
num
be
r
5
a
utosom pi
ece
s som
e
tim
e
s
e
xp
e
ri
e
n
ce
tr
a
nslo
ca
tion with
a
utosom
e
s
N
um
be
r
15
.
W
olf
-
H
irs
c
hhorn syn
d
rom
e
is
ca
us
ed b
y
de
l
e
tion on
c
hromosom
e
num
be
r
4
(
4
P
),
r
e
sulting in f
e
t
a
l growth
ba
rri
e
rs
,
hypoth
e
l
e
rs
,
a
pp
ea
r
a
n
ce
of
a
typi
ca
l f
ace
,
s
e
v
e
r
e
int
e
ll
ec
tu
a
l
d
is
ab
ility
,
a
n
d
s
ca
lp
de
f
ec
ts in th
e
post
e
rior mi
d
lin
e
(
a
pl
a
si
a
kutis
).
P
r
ade
r
-
W
illi
'
s syn
d
rom
e
is
a c
hromosom
e ab
norm
a
lity
d
u
e
to mi
c
ro
de
l
e
si in th
e
15
Q
11
-
13
c
hromosom
e
,
o
cc
urs wh
e
n th
e
g
e
n
e
from th
e
s
a
m
e
lo
c
us from moth
e
r or
f
a
th
e
r r
e
v
ea
ls
a d
iff
e
r
e
nt g
e
n
e e
xpr
e
ssion
.
I
n th
e ca
s
e
of
P
r
ade
r
-
W
illi
,
De
l
e
si is
p
a
t
e
rn
a
l
.
T
his syn
d
rom
e
is
ca
us
ed b
y
a
pro
b
l
e
m in th
e
g
e
n
e
in
c
hromosom
e
15
whi
c
h
d
isrupts th
e
fun
c
tion of th
e
hypoth
a
l
a
mus
,
r
e
sulting in un
c
ontroll
ed
hung
e
r
,
th
e
growth is h
a
mp
e
r
ed
,
s
e
xu
a
l r
e
t
a
r
da
tion
,
a
n
d
oth
e
r pro
b
l
e
ms su
c
h
a
s s
c
oliosis
.
A
ng
e
lm
a
n
'
s syn
d
rom
e
,
e
xpl
a
in
ed b
y
D
r
.
Ha
rry
A
ng
e
lm
a
n in
1965
,
is
a
g
e
n
e
ti
c
d
isor
de
r th
a
t is oft
e
n
ca
us
ed b
y th
e
pro
b
l
e
m in th
e
u
be
3
a
g
e
n
e
in
c
hromosom
e
15
.
I
n most
ca
s
e
s
,
th
e
u
be
3
a
g
e
n
e
from moth
e
r is not
ac
tiv
e
or
da
m
a
g
ed
.
S
ymptoms of
A
ng
e
lm
a
n syn
d
rom
e
in
c
lu
de de
l
a
ys in
de
v
e
lopm
e
nt
,
sp
eec
h
d
isor
de
rs
,
ba
l
a
n
ce
pro
b
l
e
ms
,
b
o
d
y mov
e
m
e
nts th
a
t oft
e
n tr
e
m
b
l
e
,
oft
e
n smil
e
,
s
e
izur
e
s
,
sm
a
ll h
ead
s
,
un
c
oor
d
in
a
t
ed e
y
e
mov
e
m
e
nts
,
a
n
d
hypopigm
e
nt
a
tion
.
D
upli
ca
tion is
a c
on
d
ition in whi
c
h p
a
rt of th
e c
hromosom
e e
xp
e
ri
e
n
ce
s g
e
n
e
r
e
p
e
tition
.
A
lthough
d
upli
ca
tion usu
a
lly
ca
us
e
s s
e
v
e
r
e ab
norm
a
liti
e
s or l
e
t
a
l in
hum
a
ns
,
som
e
tim
e
s it
ca
n
be
foun
d
in
c
hil
d
r
e
n with v
a
rious typ
e
s of
ab
norm
a
liti
e
s
.
D
upli
ca
tion is oft
e
n
acc
omp
a
ni
ed b
y
c
hromosom
e de
fi
c
i
e
n
c
y
.
I
nv
e
rsion is
a c
on
d
ition in whi
c
h th
e
s
e
qu
e
n
ce
of g
e
n
e
s on th
e
r
e
v
e
rs
e c
hromosom
e
s
ec
tion
.
Pa
r
ace
ntri
c
inv
e
rsion o
cc
urs wh
e
n
ce
ntrom
e
rs
a
r
e
outsi
de
th
e
ins
e
r of th
e
inv
e
rsion
,
whil
e
p
e
ris
e
ntri
c
inv
e
rsion o
cc
urs wh
e
n th
e ce
ntrom
e
r
e
is in th
e
ins
e
r of
th
e
ins
e
r
.
I
nv
e
rsion o
cc
urs
a
ft
e
r
a b
rok
e
n
c
hromosom
e
in two pl
ace
s
a
n
d
th
e
n
r
e
j
ec
ts in
a
n upsi
de d
own position
.
T
r
a
nslo
ca
tion is th
e
mov
e
m
e
nt of
c
hromosom
e
m
a
t
e
ri
a
l from on
e c
hromosom
e
to
a
noth
e
r
c
hromosom
e
.
I
f not
acc
omp
a
ni
ed b
y loss of
DNA
m
a
t
e
ri
a
l
,
ca
ll
ed Ba
l
a
n
ced
T
r
a
nslo
ca
tion
.
I
nst
ead
,
U
n
ba
l
a
n
ced T
r
a
nslo
ca
tion involv
e
s losing
DNA
m
a
t
e
ri
a
l
.
Re
siph
a
l tr
a
nslo
ca
tion involv
e
s
e
x
c
h
a
ng
e
s of fr
a
gm
e
nts
be
tw
ee
n two
c
hromosom
e
s
,
whil
e R
o
be
rtsoni
a
n tr
a
nslo
ca
tion o
cc
urs
d
u
e
to fusion of two
-
b
rom
e
ntri
c
c
hromosom
e
s su
c
h
a
s
c
hromosom
e
13
,
14
,
15
,
21
a
n
d
22
.
I
so
c
hromosom
e
is
a c
on
d
ition in whi
c
h on
e c
hromosom
e a
rm
e
xp
e
ri
e
n
ce
s
de
l
e
tions
a
n
d
is r
e
pl
aced
with
d
upli
ca
t
e
s from oth
e
r
a
rms
,
so th
a
t th
e
two
c
hromosom
e a
rms
look i
de
nti
ca
l
.
I
so
c
hromosom
e
s
ca
n o
cc
ur
d
u
e
to f
a
ilur
e
in th
e
s
e
p
a
r
a
tion of
ce
ntrom
e
rs in m
e
iosis
II
,
a
lthough this is r
a
r
e
.
I
so
c
hromosom
e
s
a
r
e
oft
e
n foun
d
in
p
a
ti
e
nts with
T
urn
e
r syn
d
rom
e
,
e
sp
ec
i
a
lly on th
e
long sl
ee
v
e
s of
C
hromosom
e X
.
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