遗传归纳.docVIP

Patterns of inheritance Index case/proband/propositus/proposita: The family tree begins with the person through whom the family came to the attention of the investigator. Determining the patterns: family analysis, index case, pedigree drawing Autosomal inheritance: A trait or disorder that is determined by a gene on an autosome. Sex-linked inheritance: A trait or disorder determined by a gene on one of the sex chromosomes. Heterozygous state: A person posseses both an abnormal or mutant allele and the normal allele. Pleiotropy: A single gene that may give rise to two or more apparently unrelated effects. Dominant pedigree features: affect both male and female in equal proportion. affects multiple generations. transmitted by both sexes. Variable expressivity: The clinical features in autosomal dominant disorders can show striking variation from person to person, even in the same family. Redeuced penetrance: In some individuals heterozygous for gene mutations giving rise to certain autosomal dominant disorders there may be no abnormal clinical features. Co-dominance: Two allelic traits that are both expressed in the heterozygous state. Autosomal recessive inheritance: affects male and female in equal proportions. usually only affects one sibling and only in one generation. consanguinity Pseudodominance: If an individual who is homozygous for an autosomal recessive disorder has children with a carrier of the same disorder, their offspring have 50%chance of being affected. Locus heterogeneity: A disorder inherited in the same manner can be due to mutations in more than one gene. X-linked recessive inheritance pedigree features: affects males almost exclusively; from heterozygous females to hemizygotes male; no male-to-male transmission. Disease:hemophilias, Duchenn muscular dystrophy, red-green color blindness, ocular albinism, Manifesting heterozygote: The skewed X-inactivation happened, the active X chromosome in most of the cells of a heter