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PEDIGREES & Sex-Linked Traits & Disorders
Me Father Father’s Father Father’s Paternal Grandfather Father’s Paternal Grandmother Father’s Mother Father’s Maternal Grandfather Father’s Maternal Grandmother Mother Mother’s Father Mother’s Paternal Grandfather Mother’s Paternal Grandmother Mother’s Mother Mother’s Maternal Grandfather Mother’s Maternal Grandmother PEDIGREES & Sex-Linked Traits & Disorders
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What is a Pedigree? A pedigree is a chart, similar to a family tree, that follows traits throughout generations.
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Symbols Each symbol in a pedigree has a meaning.
Males are represented by squares Females are represented by circles If a person’s square or circle is empty, or not shaded in, then they do not carry the trait that is being analyzed in the pedigree. However, if someone is affected by the trait being analyzed, then their square or circle is completely shaded in.
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Carriers OTHER SYMBOLS
A carrier is someone that carries the trait being analyzed, but does not exhibit the trait in question. Essentially, a carrier is heterozygous. A carrier’s square or circle is filled in half way to show that they carry, but do not exhibit, the trait in question. OTHER SYMBOLS A horizontal line joining shapes indicates marriages A bracket from the marriage line indicates children
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Sex-Linked Traits vs. Autosomal Traits
Autosomal traits have to do with body chromosomes Sex-linked traits have to do with the sex chromosomes. Sex-Linked traits or disorders, such as baldness (a trait), tend to occur more in one gender or another, while an autosomal trait or disorder tends to affect both genders evenly.
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Example of a Sex-Linked Trait Disorder
Baldness is a Sex-Linked trait that is carried on the X Chromosome. It shows up in males more often than females because females have a second X chromosome that can mask the recessive trait. Men only have the one X chromosome, so if they receive the bald gene from their mother, then they have no other X to mask the trait. Therefore, they will be bald.
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Pedigree Use Pedigrees can be used to follow traits, such as baldness, and disorders, such as Huntington’s disease, throughout generations.
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