Presentation on theme: "Pedigree Charts The family tree of genetics. Overview I.What is a pedigree? a. Definition b. Uses II. Constructing a pedigree a. Symbols b. Connecting."— Presentation transcript:
Overview I.What is a pedigree? a. Definition b. Uses II. Constructing a pedigree a. Symbols b. Connecting the symbols III. Interpreting a pedigree
What is a Pedigree? A pedigree is a chart of the genetic history of family over several generations for a particular trait. Can be used: –to discover the inheritnace pattern of a disease or disorder (autosomal versus sex-linked, dominant vs. recessive) –Along with punnett squares to determine genotype and phenotypes probabilities
Constructing a Pedigree - Gender symbols Male Female
Connecting Pedigree Symbols Married couple (or parents of a child) Siblings
Connecting Pedigree Symbols Fraternal twins (do not have identical DNA) Identical twins (DO have identical DNA) Twins :
Symbols in a Pedigree Chart Affected X-linked carrier Autosomal carrier Deceased
Interpreting a Pedigree Chart 1. Determining if the pedigree chart shows an autosomal or X-linked disorder/ disease X-linked disorders occur on the X chromosome (remember males have only 1 X chromosome) Autosomal disorders occur on the other chromosomes (pairs 1-22)
Therefore… If more of the males in the pedigree are affected the disorder is X- linked If there is not a significant difference in # of males and females the disorder is autosomal.
Example of Pedigree Charts Example A: Autosomal or X-linked?
Interpreting a Pedigree Chart 2.Determining whether the disorder is dominant or recessive –If the disorder is dominant, one of the parents of an affected individual must have the disorder. –If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous (carriers).
Summary Pedigrees are family trees that illustrate genetic history. To begin to interpret a pedigree, determine if the inheritance pattern of the disorder/disease (autosomal or X-linked & dominant or recessive) Pedigrees can be used to find out the probability of a child having a disorder in a particular family.