Human Karyotype Analysis
Down Syndrome: 47, in 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 Fig Cummings, Human Heredity, 6th ed.
Fig Singer, Human Genetics, 2nd edition 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.
Patau Syndrome: 47, 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, 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 , Human Heredity, Michael R. Cummings, 4 th edition
1 in 10,000 female births short stature wide chest extra skin folds on neck Turner Syndrome: 45, X underdeveloped sexual characteristics rudimentary ovaries, sterile no mental retardation is associated with this syndrome Figs. 6.18, Human Heredity, Michael R. Cummings, 6 th edition
Figs. 6.20, Human Heredity, Michael R. Cummings, 6 th edition Klinefelter Syndrome: 47, XXY 1 in 1000 male births underdeveloped testes, sterile male genitalia feminization of 2 o sexual characteristics mental retardation with more severe forms (XXXY, XXXXY)
Down Patau Edwards Turner, Klinefelter 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
Fig. 6.2, Cummings, Human Heredity, 2nd edition Gene Dosage and Gene Balance are both Important
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