![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Cystic fibrosis, 95, 96. See also Birth defect, occurrence of twins as
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Daniels, Michael, 74
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Depression, in female twins, 140, 141
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Derom, Catherine, 98
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Determinism, 78. See also Behavioral genetics
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Devlin, Bernie, 73, 74, 75
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Diamond, Milton, 116, 117
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Divorce
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | environmental factors, 150, 151-152
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | heritability of, 150-151, 152
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | and identical twins, 150-151, 154
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Dizygotic (DZ) twins. See Fraternal twins
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![](/files/03/02/28/f030228/public/bd014e5cf10977d319edfaab72ea3d1a.gif) | Dopamine, 80
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