Pedigrees
•What is a Pedigree?
•
A pedigree is a diagram of family relationships that uses symbols to
represent people and lines to represent genetic relationships. These
diagrams make it easier to visualize relationships within families, especially
large extended families.
•
Pedigrees are often used to determine the mode of inheritance (dominant,
recessive) of genetic diseases.
•
Squares represent males.
•
Circles represent females.
•
Horizontal lines linking a
•
male and female represent
•
mating. Vertical lines
•
extending downward from
•
a couple represent their children.
•
If the purpose of a pedigree is to analyze the pattern of
inheritance of a particular trait, it is usual to shade in this trait.
•
Infected male
In this pedigree: the grandparents
had three children, two boys and
one girl. The daughter married and
Produced two grandchildren, both
boys.
The grandfather has the trait. The daughter is a carrier. One of
the grandsons has the trait.
•Types of Inheritance
•
There are four types of inheritance patterns that we will be
analyzing:
•
1.
2.
3.
4.
•
•
•
autosomal dominant
autosomal recessive
X – linked dominant
X- linked recessive
•Autosomal Dominant
•
•
A – has the trait
a – normal (no trait, recessive)
• Autosomal Recessive
• A – normal ( no trait, recessive)
• a – has the trait
• X – Linked Dominant
• XA – has the trait
• Xa – normal
•
Y – Y chromosome (males only)
• X – Linked Recessive
• XA – normal
• Xa – has the trait
• Y – Y chromosome (males only)
•Locus
•
The location of a gene.
•
For example, the locus of the gene OCA1 (or Oculocutaneous
Albanism Type 1, the gene associated with albinism) is on
11q1.4-2.1, which means it is on the long arm of chromosome
11, between sub-band 4 of band 1 to sub-band 1 of band 2.