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Table 1 Sex chromosome dosage and phenotypes in humans and D. melanogaster

From: Sex-biased chromatin and regulatory cross-talk between sex chromosomes, autosomes, and mitochondria

Genotype Human gonadal sex Human phenotype Fly gonadal sex Fly phenotype
XO Female Turner femalea Male Sterile male
XX Female Female Female Female
XY Male Male Male Male
XXY Male Klinefelter maleb Female Healthy female
XYY Male Slightly atypical malec Male Lesser characterized male
XXX Female Slightly atypical femaled Female Metafemalee
  1. ‘Male’ and ‘female’ designations are based on gonadal sex. aXO (Turner) females have female external genitals but often have non-functioning ovaries, lack a menstrual cycle, and are sterile. Prevalence is estimated to be 1 per 2,000 live-born females[68]. bXXY (Klinefelter) males have male genitals but are often sterile and hypogonadic. They may display a range of female secondary characteristics, including enlarged breasts and small or undescended testes. Prevalence is estimated to be 1 per 658 live-born males[69]. cPrevalence of XYY males is estimated to be 1 in 1,000, but approximately 85% are never diagnosed. The phenotype commonly includes tall stature, macroenchephaly, macroorchidism, decreased muscle tone, and an increase in autistic spectrum disorder. Some may be at risk of reduced fertility[70]. dTriple X syndrome in females has a variable phenotype, and XXX females will often not display any abnormalities. The prevalence is about 1 per 1,000 female births[71]. eMetafemale Drosophila are often sterile and can display narrowed abdomens, wing abnormalities, irregular eye facets, and/or malformed legs. The observed frequency in adults is less that 1%, and viability post-eclosion is limited[7275].