Pedigree Drawing and Analysis

• Starts with the person through whom the family came to medical (genetic) attention

• Has a codified shorthand• Standardization of symbols generally

adopted• Information obtained historically or by

ongoing evaluation– updatable – allows a pattern of inheritance of a trait to be

determined– useful for linkage analysis (see later lecture)

Male

Female

Phenotypic/genotypic affected

Used to mark the proband (index case)

Lines are used to link individualsHorizontal lines between symbols denote matingVertical lines mark parent/child relationships

Birth order is left = oldest, right = youngestTwins have special notation

Sex unknown

Numerals in symbols indicate number of sibs of same sex

Roman Numerals indicate GenerationsArabic numerals identify individuals within a generation

1 2

II

2 3

I

1 4

1 2

II2 3

I

1 4

III

What is the inheritance pattern and why?

What pattern of inheritance is shown?

What additional information might molecular, biochemical or chromosomal techniques reveal?

What pattern of inheritance is present?Can additional information be deduced about individuals in each generation?

X linked lethal? or X-linked recessive?

The pedigree indicates the individuals who have hadsymptoms of acute porphyria.

However, biochemical testing reveals this pedigree.What principle is being demonstrated?

What pattern of inheritance is present?What can you tell person III 4?