Transcript PEDIGREE CHARTS

PEDIGREE
CHARTS
A family history of genetics
Edited from the original produced by Paul Billiet
[http://www.saburchill.com/IBbiology/bio_hp.html]
What is a pedigree chart?
a diagram that shows the appearance of a
particular gene from one generation to the
next
 can be used to study the inheritance of a
hereditary condition (like cystic fibrosis)
 are particularly useful when there are large
families and a good family record over
several generations.

Symbols Used in Pedigree Charts
male
female
A marriage with five children, two
daughters and three sons.
Vertical lines connect
children to their
parents
A solid square or
circle indicates that
the person has a
certain trait
Oldest child  Youngest child
A half-filled square or circle indicates
that the person is a carrier of the
trait.
Organizing the Pedigree Chart
A pedigree chart of a family showing 20 individuals
Organizing the Pedigree Chart
Generations are identified by Roman numerals
I
II
III
IV
Organizing the Pedigree Chart
Individuals in each generation are identified by
Arabic numerals numbered from the left
I
1
II
III
IV
1
1
2
3
2
3
2
4
5
7
6
4
5
1
2
6
3
4
5
Organizing the Pedigree Chart
In this example, let’s look at a recessive trait like light eyes.
Individuals II3, II6, IV2, and IV3 have light eyes.
The carriers (of the recessive gene) are I1, I2, III5, and
III6.
I
1
II
III
IV
1
1
2
3
2
3
2
4
5
7
6
4
5
1
2
6
3
4
5