3 2 8 Perform An Investigation To Construct Pedigrees Or Fam

Pedigrees ( I always imagine the dog food brand)

What is a pedigree?

  • Chart of genetic history of family over several generations
  • Used to analyse family history (similar to punnet squares)

Symbol Key


Retracing recessive defects and affected chromosomes

1. Determining if the defect is autosomal or X-lined (sex-linked)

  • If most of the males in the pedigree are affected by the disorder – X-linked
  • If it is an even split (50/50 ratio) between males and females the disorder is autosomal

2. Dominant/Recessive

  • If the disorder is dominant, one parent must express it in the phenotype
  • if the disorder is recessive, neither parent will express it –> Can be heterozygous

- Nathaniel Tran
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