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Patterns of Inheritance i n Humans

Patterns of Inheritance i n Humans. Pedigree. Geneticists study the inheritance of certain traits by using a Pedigree A pedigree is a visual representation of a family and shows inheritance patterns over several generations. Can be used to determine genotype Why do we need pedigrees?.

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Patterns of Inheritance i n Humans

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  1. Patterns of Inheritancein Humans

  2. Pedigree • Geneticists study the inheritance of certain traits by using a Pedigree • A pedigree is a visual representation of a family and shows inheritance patterns over several generations. • Can be used to determine genotype • Why do we need pedigrees?

  3. Autosomal Inheritance • Most traits and genetic disorders are coded on autosomal chromosomes. • Traits and disorders can be autosomal dominant or autosomal recessive.

  4. Huntington’s Disease • Autosomal Dominant • Causes Brain to deteriorate over 15 years

  5. Cystic Fibrosis • Autosomal Recessive • Mucus buildup causes breathing and digestive problems.

  6. Moving Beyond Mendel • Mendel’s experiments only considered traits to be dominant or recessive • Sometimes both traits are expressed and sometimes the trait is an intermediate of the parental traits

  7. Incomplete Dominance • A situation when neither allele for a trait can completely mask the other. • Heterozygote's have a phenotype in-between that of their parents

  8. Codominance • Both alleles are fully expressed

  9. Codominance in Humans • Ex: Sickle Cell Anemia • Homozygous recessive individuals have all sickle cells while Heterozygotes have sickle cells and normal cells. • Heterozygotes have resistance to malaria.

  10. Heterozygous Advantage • This is a situation where Heterozygotes have an advantage over homozygous dominant and homozygous recessive. • Why would having the Sickle Cell trait be an advantage?

  11. Multiple Alleles • Many traits in Humans and other species are a result of interactions between more than 2 alleles on a specific gene. • That is, there are more than just two possible phenotypes and genotypes.

  12. ABO Blood type • In Humans, Blood Type is determined by the interaction of 3 blood type alleles. • IA IB and i

  13. Polygenic Inheritance • Some traits show continuous variation and will vary gradually from one extreme to another • Traits like these are usually controlled by more than one gene and are called Polygenic Traits • The group of genes that all contribute to the phenotype are called polygenes.

  14. Skin Colour • Only the dominant forms of the gene will contribute to the phenotype.

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