Pedigree Analysis
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Workshop Outline

Two major categories of inherited genetic diseases.
        1. Autosomal
        2. Sex-linked (almost always X-linked)

Two subtypes:
        1. Recessive
        2. Dominant

Patterns for Human Genetic Diseases

Note: When trying to solve a pedigree, use these rules to guide you. Also, draw out a Punnett square; it can be very useful!

1) Autosomal Recessive

Parents are generally unaffected.
Approximately 25% of children are affected if both parents are carriers.
Two affected parents will always have an affected child.
Recessive traits often result from consanguineous mating.
(ex. ears of many people in hill country of Texas)

 

2) Autosomal Dominant

Trait occurs every generation.
When one parent is affected, approximately 50% of children will be affected.
Affected individuals are usually heterozygous.
Unaffected parents do not produce affected children.
Two affected parents can have unaffected children.

 

3) Sex-linked Recessive (X-linked)

Children of an affected male (father) will not be affected. However, 100% of the female offspring will be carriers of the disease.
An unaffected carrier female (heterozygous mother) will have approximately 50% affected male offspring and no affected female offspring (although approximately 50% of the female offspring will be carriers).

 

4) Sex-linked Dominant (X-linked)

Affected male will always produce affected female offspring and unaffected male offspring.
Affected female will produce approximately 50% affected male and 50% affected female offspring if she is heterozygous. If she is homozygous, 100% of the offspring will be affected.

 

5) Sex-linked (Y-chromosome)

Trait is always passed from father to son.
Only male offspring are affected.

THE WOMEN HAVE US ON THIS ONE!!