- Pedigree.

-A pedigree:- is a diagram of a family history and illustrates relationships among family members; it shows which family members are affected with specific medical conditions.

-Information for a three-generation pedigree should be obtained from a family being evaluated for a genetic disorder.

- The patient through whom the family is ascertained is called the proband.

(Symbols commonly used in pedigree chart)

-Consanguinty:-

There are Five degrees of Consanguinty:-

*first-degree:-
-First-degree relatives share half of their genetic material with the proband (brothers, sisters, children,parents).

*second degree:-
-Second degre relatives share one fourth of their genetic material (grandparents,aunts,uncles).

*Third degree:-
-Third degree relatives share one eighth of their genetic material with the proband(1st cousin).

*Fourth degree:-
-Fourth degree relatives share one sixteenth of their genetic material with the proband(2nd cousin).

*Fifth degree:-
-Fifth degree relatives are once remote form the proband.


References:-
(1)Richard E Behrman,Nelson Textbook of Pediatrics,17th ed,ch69,(http://www.elsevier.com).
(2)Bennett RL, Steinhaus KA, Uhrich SB, et al: Recommendations for standardized pedigree nomenclature. J Genet Counsel 1995;4:267–79.)