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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
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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 • underdeveloped sexual characteristics • rudimentary ovaries, sterile • no mental retardation is associated with this syndrome • 1 in 10,000 female births • short stature • wide chest • extra skin folds on neck
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)
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 Patau Edwards Turner, Klinefelter Down
Gene Dosage and Gene Balance are both Important Fig. 6.2, Cummings, Human Heredity, 2nd edition
