Human pedigree

1. Pedigree Analysis

2. Pedigree symbols
Female
Male
Gender
unknown
Deceased
3
n
P

3.  Stillborn
 Spontaneous
abortion/Miscarriage
 Termination of pregnancy
elective reasons
 Termination of pregnancy
genetic/affected condition
SB

4.  Affected individual
 Proband
• 1st person in family to
come to medical/genetic
attention
 Obligate carrier
 Infertility

5. Constructing the Pedigree
 Relationship or
marriage
 Break in
relationship
 Consanguineous
relationship

6.  Monozygotic
twins
• (Identical)
 Dizygotic twins
• (Fraternal)

7.  Adoption
into a family
 Adoption out
of a family

8.  Include below
gender symbol
name, maiden name
if married &
birthdate or age
 Generations are
symbolized by
Roman numerals
 Should give current
date on pedigree
John Smith
10-1-49
I.
Current date:
08-31-06

9. Other Abbreviations
 d. 79y
 dx. 41y
 Died at 79 years of
age
 Diagnosed at 41 years
of age

10.  Siblings are
drawn left to
right in birth
order
I.
II.
III.

11. Rules of Thumb
 Always include a key
 At least 3 generations
 Use birth dates or ages
 Sign and date
 Include ancestry with oldest generations

12.  Causes of
death or health
problems
should be
noted on the
pedigree or
explained by a
key
Key
Hypertension
Breast cancer
52

13. Autosomal Dominant Inheritance
 Each affected individual has one affected
parent
 Males and females may be affected
 Pattern of inheritance is vertical (passed
from generation to generation)

14.  Autosomal
Dominant
Inheritance
I.
II.
III.

15. Autosomal Recessive Inhertance
 Do not need a parent who is affected; each
parent must be a carrier of the recessive
gene
 Males and females may be affected
 Pattern of inheritance is horizontal (usually
seen in siblings)
 Offspring of parent with the condition are
obligate carriers

16.  Autosomal
Recessive
Inheritance
I.
II.
III.

17. X-Linked Inhertance
 Gene is located on X chromosome
 Female is usually clinically normal and
disorders are typically seen more often in
males than females
 Absence of male-to-male transmission

18.  X-Linked
Inheritance
I.
II.
III.