Genotypic sex

The two major types of genotypic sex determination, the mammalian and the avian types, can be referred to as XX/XY or ZZ/ZW, respectively. In animals expressing the XX/XY system, the male is the heterogametic sex (XY) while the female is homogametic (XX). The avian equivalent to the Y-chromosome of mammals is designated by the letter W, and the X-chromosome denoted by the... 

Genotypic sex determination occurs in reptiles in a variety of different forms. In snakes, the female is heterogametic (analogous to the XY chromosome pairing in male mammals), whereas either the male or the female in some species of turtles and lizards is heterogametic sex. Still other lizards have genotypic sex determination... 

SCA affects both males and females equally because it is not a sex-linked disease. Nine percent of African Americans possess the SCT and 1 in 600 has HbSS.5 Two thousand infants are identified with SCD annually in the United States.6 For every infant diagnosed with SCD, 50 are identified as carriers.6 HbSS (approximately 45%) is the most common genotypic expression, followed by HbSC (approximately 25%), HbS/5+-thalassemia (approximately 8%), and HbS/3° thalassemia (approximately 2%). Other variants account for less than 1% of patients.3,6... 

Bickeboller H, Campion D, Brice A, Amouyel P, Hannequin D, Didierjean O et al. Apolipoprotein E and Alzheimer disease genotype-specific risks by age and sex. Am J Hum Genet 1997 ... 

Hatchell PC, Collins AC. The influence of genotype and sex on behavioural sensitivity to nicotine in mice. Psychopharmacology 1980 71(1) 45—49. Robinson SF, Marks MJ, Collins AC. Inbred mouse strains vary in oral self-selection of nicotine. Psychopharmacology 1996 124(4) 332—339. 

Farrer, L. A., Cupples, L. A., Haines, J. L. et al. Effects of age, sex, and ethnicity on the association between apolipoprotein E genotype and Alzheimer disease, a meta-analysis. APOE and Alzheimer Disease Meta Analysis Consortium. J.A.M.A. 278 1349-1356, 1997. 

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