Transcript PEDIGREE CHARTS

PEDIGREE CHARTS
A family history of a genetic condition or trait
WHAT IS A PEDIGREE CHART?
 Pedigree
charts show a record of the
family of an individual.
 They can be used to study a hereditary
condition or trait.
 They are especially useful when there
are large families that cover several
generations.
© 2007 Paul Billiet ODWS
STUDYING HUMAN GENETICS
Today
genetic engineering has
new tools to offer doctors studying
genetic diseases
A genetic counselor will still use
pedigree charts to help determine
the distribution of a disease in an
affected family
© 2007 Paul Billiet ODWS
ORGANIZING A PEDIGREE CHART
 Generations
are identified by Roman
numerals & are on different levels.
I
II
III
IV
 Males
are represented by the square
Females are represented by the circle

I
II
III
IV
 Parents
are connected with a
horizontal line.
 Offspring are below the parents and
the bracket is connected by a vertical
line.
 Siblings are within the same bracket.
READING THE SYMBOLS USED IN
PEDIGREE CHARTS

Normal male

Affected male

Normal female

Affected female
A marriage with five children, two
daughters and three sons. The middle
son is affected by the condition.


Marriage
Eldest child  Youngest child
© 2007 Paul Billiet ODWS
SEX LINKED DISORDER:
COLOR-BLINDNESS
Hemophilia is a blood
disorder that affects
blood clotting.
It comes from a
recessive gene on the
x-chromosome.
Use the pedigree
chart on worksheet to
trace hemophilia
through the Royal
family.
CLOSURE:
1. Explain how you can determine if a person is
affected by a specific condition by looking at
a pedigree chart.
2. Explain what it means when a trait is “xlinked”
3. Is it possible to be a carrier for a gene that
codes for a disorder without showing any
symptoms? How?