Nail-biting in twins.
D000293:Adolescent; D000367:Age Factors; D001789:Blood Group Antigens; D002648:Child; D004200:Diseases in Twins; D005260:Female; D005386:Fingersucking / Q000150:complications; D006801:Humans; D008297:Male; D009259:Nail Biting / Q000150:complications / Q000235:genetics*; D012737:Sex Factors
D001789:Blood Group Antigens