How accurate are genetic pedigrees?

Often incomplete: A pedigree is a standard diagram of your family history, using squares for males, circles for females, joining lines for marriage and offspring. Traits/diseases are indicated by marking the circles or squares, the patterns revealing inheritance mechanisms. Accuracy depends on completeness of family information and the knowledge/experience of the historian/interpreter (think clinical geneticist).

Depends: it depends, like most things, on who is doing it. see out reputable companies.