Title: PEDIGREE CHARTS
1PEDIGREE CHARTS
- A family history of a genetic condition
Pages 1-3 6-9 taken from Paul Billiet at the
following website saburchill.com/IBbiology/.../im
ages/05PEDIGREE CHARTS.ppt
2What is a pedigree chart?
- Pedigree charts show a record of the family of an
individual - They can be used to study the transmission of a
hereditary condition - They are particularly useful when there are large
families and a good family record over several
generations.
3Studying human genetics
- You cannot make humans of different types breed
together - Pedigree charts offer an ethical way of studying
human genetics - Today genetic engineering has new tools to offer
doctors studying genetic diseases - A genetic counsellor will still use pedigree
charts to help determine the distribution of a
disease in an affected family
4Sex on a Pedigree
5Connecting Lines
- Marriage horizontal line between two people
- Siblings horizontal line above boxes
- Twins
- Fraternal
- Identical
-
Children are listed from youngest to oldest (left
to right)
6Symbols used in pedigree charts
- Normal male Affected male
- Normal female Affected
female - or autosomal carrier
(heterozygote ) - x-linked carrier
- or deceased
7Organizing the pedigree chart
- A pedigree chart of a family showing 20
individuals
8Organizing the pedigree chart
- Generations are identified by Roman numerals
9Organizing the pedigree chart
- Individuals in each generation are identified by
Arabic numerals numbered from the left - Therefore the affected individuals are II3, IV2
and IV3
10Reading a Pedigree Chart
- Autosomal or x-linked trait?
- If the affected are mostly males then the trait
is x-linked - If the affected is a fairly even ratio between
males and females then the trait is autosomal
11Autosomal or X-linked?
12Autosomal
13Determining Dominant or Recessive Trait?
- If the disorder is dominant one of the parents
must have the disorder - If the disorder is recessive then neither of the
parents HAS to have the trait because they are
heterozygous. However one of both may have the
disorder
14Dominant or recessive?
15Dominant
16Dominant or Recessive?
17Recessive
Some times carriers are not listed as a half
filled in square/circle. You must interpret the
pedigree
18Pedigrees
- Remember.
- you must READ and INTERPRET the pedigree.