Pedigree analysis 2-1
The study of an inherited trait in a group of related individuals to determine the pattern and characteristics of the trait, including its mode of inheritance, age of onset, and phenotypic variability. First suggested by galton.
- Symbols
- Draw a family tree. Start with effective person. Then siblings. Parents. Maternal and paternal relatives.
- Reliance on principles of mendelian genetics. Law of dominance. Segregation. Independent assortment. One gene one character
- Major types
- Autosomal dominant inheritance. Affected children usually have affected parents. Heterozygotes are affected. Male and female children affected in equal frequency. To affected parents can have on affected children. Polydactyly. Cold urticaria.
- Autosomal recessive. Cystic fibrosis. Deaf mutism. Most affected children have normal parents. Heterozygous have normal phenotype. Both Affected parents always have affected children. One affected parent children may not be affected. Affects male and female in equal. Increases with consanguineous marriages
- X linked recessive. Rare in Pedigree. Fathers do not pass on to their sons. Might skip generations. Males more affected than females. Sons of carrier female have 50% chance of being effected while daughters have 50% chance of being a career. Haemophilia. Colour blindness. Daughters of affected mails are always career.
- X linked dominant. common in Pedigree frequency. Father transmits to all the daughters. Male females equally affected. Goltz syndrome. Vitamin d resistant rickets.
- Application. Genetic counselling. Genetic screening for abortion. Paternity dispute. Studying mendelism.