Human
Karyotype Analysis
Down Syndrome: 47, +21
Fig. 6.15 Cummings, Human Heredity, 6th ed.
1 in 600-700 births
epicanthic fold of skin over corner of each eye
wide, flattened skull
protruding, furrowed tongue causes mouth to remain partially open
retarded growth and mental development
fertile
The incidence of Down
syndrome increases from
1 in 1000 births to over
10 in 1000 births for
women over 40 years of
age
No such correlation
exists with the age of
the father. Thus, it is
believed that most cases
of Down syndrome are
the result of mistakes
made during egg
formation.
Fig. 1-20 Singer, Human Genetics, 2nd edition
Patau Syndrome: 47, +13
1 in 15,000 live births
cleft lip and palate
eye defects, polydactyly
malformation of internal organs
(brain, nervous system, heart)
survival rarely past 1 year
Edwards Syndrome: 47, +18
1 in 11,000 births
small at birth, growth retarded
malformed hands and feet
heart malformations
death within first year usually caused
by heart failure or pneumonia
Figs. 6.11 - 6.12, Human Heredity, Michael R. Cummings, 4th edition
Turner Syndrome: 45, X
Figs. 6.18, Human Heredity, Michael R. Cummings, 6th edition
•
•
•
•
1 in 10,000 female births
short stature
wide chest
extra skin folds on neck
• underdeveloped sexual
characteristics
• rudimentary ovaries, sterile
• no mental retardation is associated
with this syndrome
Klinefelter Syndrome: 47, XXY
Figs. 6.20, Human Heredity, Michael R. Cummings, 6th edition
•
•
•
•
•
1 in 1000 male births
underdeveloped testes, sterile
male genitalia
feminization of 2o sexual characteristics
mental retardation with more severe forms (XXXY, XXXXY)
Patau
Edwards
Turner, Klinefelter
Down
No other extra
chromosome karyotypes
are found - not
because they aren’t
formed, but because
their effects are too
severe to survive
development.
An estimated 20-50%
of all human
conceptions end in
spontaneous abortion 50% of those are due
to abnormal
chromosome numbers
GENE DOSAGE IS
IMPORANT
Gene Dosage and
Gene Balance are
both Important
Fig. 6.2, Cummings, Human Heredity, 2nd edition
CM
KNN2
MD
SB
SN
SP
TW1
TW2
KNN1
RO
LAD
ZC
SS
Dr. E