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Pedigree Analysis

Pedigree of Queen Victoria. Pedigree Analysis. Have you ever seen a family tree… do you have one?? Graphic representation of family inheritance. What is a pedigree? . A chart that shows a pattern of inheritance in a family for a specific trait (phenotype)

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Pedigree Analysis

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  1. Pedigree of Queen Victoria Pedigree Analysis Have you ever seen a family tree… do you have one?? Graphic representation of family inheritance.

  2. What is a pedigree? • A chart that shows a pattern of inheritance in a family for a specific trait (phenotype) • Why would we want to use a pedigree in genetics? • Track the occurrence of diseases such as: • Huntington’s – simple dominant – lethal allele – causes breakdown of the brain • Cystic fibrosis – 1/2500 – mucus accumulates (white North Amer.) • Tay-Sachs disease – lipids accumulate in CNS (Jewish) • Phenylketonuria – missing enzyme causes problems in CNS (Nordic/Swedish)

  3. The Symbols used:

  4. Sample pedigree: • generations are numbered with Roman Numerals • oldest offspring are on the left How many males are present? How many females? How many females show the trait being studied? What is the sex of offspring III-9? How many offspring did the generation I parents have? What is the difference between the II-3 & 4 and IV-2 & 3?

  5. Inheritance patterns: • Autosomal dominant: • The disease occurs in consecutive generations(does not skip a generation) • Males and females are affected, with the same probability. • Ex.: Polydactyly • Huntington’s disease

  6. Fig. 14-17 Parents Dwarf Normal Dd dd  Sperm D d Eggs dd Dd d Dwarf Normal Dd dd d Normal Dwarf

  7. Inheritance patterns: • Autosomal recessive • Males and females are equally likely to be affected. • The trait is characteristically found in siblings, not parents of affected • It generally skips a generation Parents of affected children may be related. • Ex. : Cystic fibrosis • Tay-Sach’s disease

  8. Fig. 14-16 Parents Normal Normal Aa Aa  Sperm a A Eggs Aa AA Normal (carrier) A Normal Aa aa Normal (carrier) a Albino

  9. Inheritance patterns: • Sex-linked recessive conditions • The disease is never passed from father to son.Males are much more likely to be affected than females. • All affected males in a family are related through their mothers.It generally skips a generation • Ex.: - Colour-blindness • Hemophilia

  10. Human disorders • Testing: •amniocentesis •chorionic villus sampling (CVS) • Examination of the fetus with ultrasound is another helpful technique

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