The symbols and rules to construct a pedigree using standardized human pedigree nomenclature can be found in the American Journal of Human Genetics 56:745-752 (1995). The following tutorial describes only basic symbols and rules. For complex family situations, please refer to the above journal article and/or visit the American Society for Human Genetics family history url: http://www.ashg.org/genetics/ashg/educ/007.shtml

The basics

Pregnancies are drawn as triangles, or diamonds with a capital 'P' in the center (if the sex of the pregnancy is known, a square or circle with a 'P' can be used). Twins (or triplets) are drawn like cherries off of the sibship line. Individuals who have passed away have a diagonal line drawn through their symbols. An individual's symbol may be shaded or hatched to show particular clinical status, which is interpreted in a legend or key. It is not uncommon to see notations next to an individual's symbol. These notations may state the individual's date of birth or other information of interest.

Below is an example of a family showing parents with their 4 children (2 girls and twin boys). The mother is pregnant (unknown sex) at 20 weeks gestation. The father had a brother (now deceased). The mother has a sister and a brother. The sister has one son. The father, his mother, his deceased brother, and one of his daughters have/had congenital ptosis. Notice that each generation can be found in the same horizontal field, horizontal lines only connect individuals involved in a union, and that siblings are connected through vertical lines attached to a common horizontal "sibling" line.