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Human Pedigrees

Explore human pedigrees that record genetic traits, analyzing patterns and applying Mendel's concepts. Discover recessive and dominant traits, their examples, and how to interpret sex-linked pedigrees. Learn about genetic counseling and available tests.

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Human Pedigrees

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  1. Human Pedigrees 12.3 pg 255

  2. Pedigrees • Family tree that records and traces the occurance of a trait in a family. • Analyze patterns • Applies Mendel’s concepts of dominant and recessive alleles. • Shapes: • Males- squares • Females- circles

  3. Pedigree traits • Individuals showing (expressing) the trait are shaded( colored in) • Recessive traits have “ee” genotypes • Pedigrees can be analyzed for recessive, dominant, and sex-linked disorders

  4. Recessive Traits • Most human genetic disorders are in this group. • Range of severity. • Examples- • Albinism- lack of pigment • TaySachs- fatal nerve disease • Cystic fibrosis- defective protein- thick mucous buildup affects breathing, digestion, liver. 1/25 people of European ancestry are affected in the U.S.

  5. Carrier • Has one allele but does not show the symptoms. • Heterozygous for the trait. • Some pedigrees show such individuals as a half shaded circle. • If two carriers have a child there is a ¼ chance the child will have the disorder.

  6. Dominant Traits • Only one allele needed to have disorder (heterozygous Aa or homozygous AA). • Less common • Disorder is in every generation • Examples- • Polydactyl- extra fingers and toes • Achondroplasia- dwarfism • All individuals are heterozygous. • Homozygous is fatal.

  7. Dominant Traits continued • Note- Dominant alleles are not found more often in populations. • Most dominant disorders are fatal before reproductive age. • Exception-Huntington’s disease- nervous disorder- no symptoms until 30s or 40s- so trait passed on to children.

  8. Sex-linked pedigrees • More men have the trait. • Review sex-linked notes

  9. Genetic Counselor • Collects and analyzes family inheritance patterns • Helps interpret genetic test results. • PKU- phenyketonuria- tells if baby is missing and enzyme to process phenylalanine. Diet is critical. • Sweat chloride test- cystic fibrosis. • More than 250 different genetic tests available. • Confidentiality and bioethics an issue

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