Autosomal and Sex
chromosome abnormalities
Sex Chromosome Abnormalities
Sex chromosome anomalies
Pattern / Name
Characteristics
Incidence
Treatment
XYY
Male; tall stature; tendency to low IQ,
especially verbal
1 in 1,000 male births
No special treatment
Female; normal appearance, menstrual
irregularities, learning
disorders, mental retardation
1 in 1,000 female births
Special education
(triple X)
1 in 1,000 male births
Hormone therapy, special education
(Kleinfelter)
Male, sterility, underdeveloped
secondary sex characteristics,
small testes, learning disorders
Female, short stature, webbed neck,
impaired spatial abilities, no
menstruation, sterility,
underdeveloped sex organs,
incomplete development of
secondary sex characteristics
1 in 3,500 female births
Hormone therapy, special education
Minor-to-severe mental retardation;
symptoms, which are more
severe in males, include delayed
speech and motor development,
speech impairments, and
hyperactivity; the most common
inherited form of mental
retardation
1 in 1,200 male births;
1 in 2,000 female births
Educational and behavioral therapies
when needed
XXX
XXY
XO
(Turner)
Fragile X
Sex chromosomes
abnormalities
KLINEFLETER SYNDROME
A male with XXY chromosomes
Exhibits some female characteristics
Such as enlarged breasts and
high pitched voice
TURNERS SYNDROME
A female with XO exhibits
a short stature, short neck,
and broad chest with
immature sex organs
XYY

If in meiosis II the Y chromosome does
not separate and is passed on to a boy
the sex chromosomes will be XYY. Boys
with this are unusually tall but have
normal fertility. Studies have also shown
that these men tend to be more violent
than a XY male.
How does it happen?
Non-disjunction can result in
abnormalities in the number of
sex chromosome. Both Klinefelter
and Turners result from nondisjunction
of either the male or female gamete.
The disjunction of the female gametes
can result in a Triple X female
Down Syndrome

Down syndrome is a chromosomal
abnormality of the 21th chromosome.
It is known as Trisomy 21 since
nondisjunction of a faulty cell division
results in an embryo with three
number 21 chromosomes instead
of two. People with down syndrome
are usually mentally retarded, shorter,
have a larger head and a short life
span (usually about 30 years).
Down syndrome- Prior to, or at, conception, a pair of number 21
chromosomes, in either the sperm or the egg, fail to separate
Karyotype of down syndrome