File 1-pedigree
Download
Report
Transcript File 1-pedigree
What is a
Pedigree…
And Nooooo it’s not Dogfood.
Biology I
Searcy Ninth Grade Center
It is a diagram that shows how a trait
is inherited through several generations.
Pedigree for the Albino Trait
Pedigree for a Sex Linked Trait
Human geneticists illustrate the inheritance of a
gene within a family by using a pedigree chart.
• Squares = males
• Circles = females
• Shaded = individual has the
•
•
•
•
trait or condition
Unshaded = individual does
not have trait or condition
Horizontal line = marriage
Vertical line = offspring,
arranged from left to right in
order of birth
Roman numerals - label
different generations
= unaffected female
= affected female
= female carrier
= unaffected male
= male affected by one trait
= male carrier
And more...
Patterns of Inheritance
By analyzing patterns of inheritance,
biologists can learn about genetic
diseases.
If a trait is autosomal, it will
appear in both sexes equally and if it is sexlinked, it is usually seen only in males.
The major use of pedigree analysis is in clinical
evaluation and counseling of patients with
inherited abnormalities.
Patterns of Recessive Traits
• May appear to “skip” generations
• Most children of normal and affected parents
are normal
• AA x aa ---> Aa
• All children of two affected parents will be
affected
• aa x aa ---> aa
Patterns of Recessive Traits
• Normal parents may produce affected
offspring
• Aa x Aa ---> 3/4 normal; 1/4 affected
Patterns of Dominant Traits
• Trait tends to appear each generation
• Normal and affected individual expected to
produce normal and affected children
(approximate 1:1 ratio)
• Affected individuals generally heterozygous if
rare trait
• Aa x aa ---> 1/2 Aa; 1/2 aa
Patterns of Dominant Traits
• At least one parent must be affected in order
for children to be affected
• Aa x aa
• Normal parents will always produce normal
offspring
• aa x aa ---> aa