Chromosomal aberrations Submitted by: Claudette Dabu Lester Santos AAPD2F
Chromosomal aberrations
Submitted by:
Claudette Dabu
Lester Santos
AAPD2F
Chromosomal aberration
A
ny change in the normal structure or number of
chromosomes; often results in physical or mental
abnormality.
Euploidy
N
ormal complement of chromosomes, which in
humans, is 2n where n is the haploid number
Chromosomal disorders
Aneuploidy
I
t is an abnormal number of chromosomes.
A
n extra or missing chromosome is a common cause of
genetic disorder
I
t occurs during cell division when the chromosome do not
separate properly between the two cells
Kinds of anueploidy
M
ONOSOMY- missing one chromosome from a pair (2n-1)
T
RISOMY- presence of three copies of a chromosome (2n+1)
T
ETRASOMY- presence of four copies of a chromosome (2n+2)
P
ENTASOMY- presence of additional three chromosomes of one type
in an otherwise diploid cell (2n+3)
klinefelter
I
t is a chromosomal condition that affects male sexual
development. Males with this condition typically have small
testes that do not produce enough testosterone, which is the
hormone that directs male sexual development before birth and
during puberty.
M
ost males with this syndrome have one extra copy of the X
chromosome in each cell.
I
n addition to affecting male sexual development,
variants of Klinefelter syndrome are associated with
intellectual disability, distinctive facial features,
skeletal abnormalities, poor coordination, and severe
problems with speech.
Down syndrome
I
t is also called Trisomy 21, it is a condition in which extra
genetic material delays in the way a child develops, both
mentally and physically.
C
ommon physical signs include:• Decreased muscle tone at birth• Flattened nose• Separate joints between the bones of the skull• Small ears, mouth• Upward slanting eyes; wide short hands with short fingers
Turner syndrome
I
t is a genetic disorder that affects a girl’s development.
The cause is a missing or incomplete X chromosome.
Girls who have it are short, and their ovaries don’t work
properly. Most are infertile. They are at risk for health
difficulties such as high blood pressure, kidney
problems, diabetes, cataracts, osteoporosis, and thyroid
problems.
O
ther physical features:• Short “webbed” neck with folds of skin from tops of
shoulders to sides of neck• Low hairline in the back• Low set ears• Swollen hands and feet
Patau syndrome
I
t is also called Trisomy 13
T
he extra copy of chromosome 13 in Patau syndrome
causes severe neurological and heart defects which
make it difficult for infants to survive.
P
hysical characteristics:• Extra fingers or toes (polydactyl)• Deformed feet (Rocker-bottom feet)• Small head (microcephaly)• Failure of the brain to divide into halves during gestation• Small eyes• Absent or malformed nose• Cleft lip/ cleft palate• Heart defects• Kidney defects
Cri-du-chat syndrome
I
t is a chromosomal condition that results when a piece of
chromosome 5 is missing. Infants with this condition often have
a high-pitched cry that sounds like that of a cat.
T
he disorder is characterized by intellectual disability and
delayed development, small head, low birth weight, weak muscle
tone in infancy, widely set eyes, low set ears, small jaw, rounded
face.
Edwards syndrome
A
lso called Trisomy 18
I
t is a chromosomal condition associated with sever intellectual
disability and abnormalities in may parts of the body.
O
ften have a low birth weight, small abnormally shaped head, small
jaw and mouth, clenched fists with overlapping fingers, heart
defects, and abnormalities of other organs.
Cat eye syndrome
A
rare condition caused by the p arm and a small section of
the q arm of chromosome 21 being present three or four
times instead of the usual two times.
T
he “Cat Eye” syndrome was coined because of the
particular appearance of the vertical colombas in the eyes
of some patients.