Analyzing Simple Pedigrees:
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A pedigree is just like a family tree except that it focuses on a specific genetic trait.  A pedigree usually only shows the phenotype of each family member.  With a little thought, and the hints below, you may be able to determine the genotype of each family member as well!

Hints for analyzing pedigrees:

1)  If the individual is homozygous recessive, then both parents MUST have at least
     one recessive allele (parents are heterozygous or homozygous recessive).

2)  If an individual shows the dominant trait, then at least one of the parents MUST have the
     dominant phenotype.  This one will be pretty obvious when you look at the pedigree.

3)  If both parents are homozygous recessive, then ALL offspring will be homozygous recessive.

NOTE:  In a pedigree, the trait of interest can be dominant or recessive.  The majority of harmful genetic conditions are only seen when an individual is homozygous recessive - examples of conditions caused by recessive alleles include cystic fibrosis (a disease of the secretory glands, including those that make mucus and sweat), Falconi anemia (a blood disorder), albinism (a lack of pigmentation), and phenylketonuria (a metabolic disorder).  Some genetic conditions are caused by dominant alleles (and may therefore be expressed in homozygous dominant or heterozygous individuals)- examples of conditions caused by dominant alleles include polydactyly (presence of extra fingers), achondroplasia (a type of dwarfism), neurofibromatosis (a nervous disorder), and a disease known as familial hypercholesterolemia in which affected individuals suffer from heart disease due to abnormally high cholesterol levels