STANDARD: DESCRIBE TECHNIQUES OF SUCH AS
CHROMOSOMAL ANALYSIS TO STUDY GENOMES OF
ORGANISMS (B.6H)
ESSENTIAL QUESTION: HOW CAN A KARYOTYPE
BENEFIT PARENTS EXPECTING AN OFFSPRING.
WHAT EACH OF THE HUMAN
CHROMOSOMES LOOK LIKE
KARYOTYPE: A PHOTOMICROGRAPH
OF
CHROMOSOMES ARRANGED ACCORDING
TO A STANDARD CLASSIFICATION
IN OTHER WORDS…

Chromosomes are digitally arranged so that they
are matched with their homologue or “partner”
chromosome.

Homologue chromosomes are the same size,
shape, and carry the same genes, and one is
inherited from each parent.

They are numbered according to size.
SEX DETERMINATION WITH KARYOTYPE
 This
karyotype has
23 exact pairs, which
means the person is
female.
 Note
that #23
chromosomes are
both X.
NORMAL HUMAN MALE

Note that #23
chromosomes are
X and Y.
IS THIS PERSON FEMALE OR MALE?
TRISOMY 21
 Abnormality
shown in
karyotype
 Note that there
are three copies
of #21
chromosome.
 This person has
Down
Syndrome.
PHOTOS OF DOWN SYNDROME
PATIENTS FROM THE NATIONAL DOWN
SYNDROME SOCIETY
CORRELATION BETWEEN MOTHER’S
AGE AND TRISOMY 21 INCIDENCE
MONOSOMY X
 Abnormality
shown in
karyotype
 Note
this
person only has
1 copy of the X
chromosome.
 This
female
has Turner’s
syndrome.
XXY MALE (EXTRA X)
CRI-DU-CHAT

Babies with the cry of the cat syndrome have a cry which
sounds like that of a cat in distress because the infant’s
larynx is improperly developed. Cri-du0chat babies are
severely mentally retarded and have a small cranium.
The incidences of this syndrome is 1 in 100,000 live
births.
Caused by a partial deletion of chromosome 5
TRISOMY 21, ONE OF THE MOST COMMON CAUSES OF MENTAL
Down’s
Syndrome
RETARDATION IS DUE TO AN EXTRA CHROMOSOME 2`. THIS RESULTS IN
A NUMBER OF CHARACTERISTIC FEATURES, SUCH AS SHORT STATURE,
BROAD HANDS, STUBBY FINGERS AND TOES, AND A WIDE ROUNDED
FACE. INDIVIDUALS WITH THIS SYNDROME HAVE A HIGH INCIDENCE OF
HEART DEFECTS AND LUKEMIA. THE AVERAGE RISK OF HAVING A
CHILD WITH DOWN’S SYNDROME IS 1 IN 750 LIVE BIRTHS. MOTHERS
IN THEIR EARLY TWENTIES HAVE A RISK OF 1 IN 1,500, WOMEN OVER
35 HAVE A RISK FACTOR OF 1 IN 70.
EDWARD’S SYNDROME

Trisomy 18 produces
severe mental
retardation and a
highly characteristic
pattern of
malformations such as
elongated skull, a
narrow pelvis, rocker
bottom feet. Nearly all
babies born with this
syndrome die in early
infancy. The
frequency of this
syndrome is 1 in 5,000
live births.
PATAU SYNDROME

This syndrome (trisomy 13)
causes severely abnormal
cerebral functions and
virtually always leads to
death in early infancy. This
baby has very pronounced
clefts of the lip and palate,
broad nose, small cranium
and nonfunctional eyes.
Heart defects and severe
mental retardation are also
part of the clinical picture.
The frequency is 1 in 15,000
live births.
TURNER SYNDROME (XO)

This is a result of
nondisjunction in
meiosis. These girls
appear normal before
puberty, but as they
grow secondary sex
characteristics do not
develop and no ova are
produced. The
frequency of this
syndrome is 1 in 2,500
live births.
KLINEFELTER SYNDROME (XXY)

This is a result of
nondisjunction in
meiosis. The
frequency of this
condition is 1 in
1,000 live male
births.
Characteristics
include a tall stature
and sterility. Men
appear normal in
other ways.
JACOBS (XYY)

A chromosome aberration
which is caused by
nondisjunction of the Y
chromosome during the
second phase of meiosis.
Occurrence is 1 in 1,000
live male births. Men with
this abnormality are tall
and have low mental
ability.
TRIPLE X

Occurs at a frequency of
1 in 1,000 female live
births. No specific
abnormalities are
associated with this
condition. The vast
majority of women with
this condition are
normal mentally and
physically and are
fertile.