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Chapter 8

Chapter 8. Section 4: Complex Patterns of Heredity. Grade 10 Biology Spring 2011. Objectives. Identify five factors that influence patterns of heredity Describe how mutations can cause genetic disorders List two genetic disorders, and describe their causes and symptoms

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Chapter 8

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  1. Chapter 8 Section 4: Complex Patterns of Heredity Grade 10 Biology Spring 2011

  2. Objectives • Identify five factors that influence patterns of heredity • Describe how mutations can cause genetic disorders • List two genetic disorders, and describe their causes and symptoms • Evaluate the benefits of genetic counseling

  3. Characters Influenced by Several Genes • Polygenic Inheritance: when several genes influence a character • May be scattered along the same chromosome or located on different chromosomes • Ex. Eye colour, height, weight, hair, skin colour (have degree of intermediate conditions)

  4. Intermediate Characters • Incomplete Dominance: individual displays a phenotype that is intermediate between two parents

  5. Intermediate Characters • Incomplete Dominance: • Ex: snapdragons • Red flower x white flower = pink flowers • Neither the red or white allele is completely dominant over another • Flowers appear pink because they have less red pigment than red flowers

  6. Three of More Alleles • Multiple Alleles: genes with three or more alleles • Ex. ABO blood groups (blood types) • Determined by 3 alleles: IA, IB, i • IA and IB are dominant over i, but not over each other • Therefore 4 different blood types: A, B, AB, O

  7. Codominance • Codominance: two dominant alleles are expressed at the same time, both forms of character are displayed • Blood type is an example • Different than incomplete dominance because both traits are displayed

  8. Characters Influenced by the Environment • An individuals phenotype often depends on conditions in the environment • Hydrangea flowers display flowers from blue to pink • Acidic soil = blue flowers • Neutral to basic soil = pink flowers • Ex. Siamese cat, arctic fox, humans

  9. Genetic Disorders • Mutation: changes in genetic material • Genetic Disorders: harmful effects produced by inherited mutations

  10. Treating Genetic Disorders • Most cannot be cured • Progress being made • Genetic counseling: form of medical guidance that informs people about genetic problems that could affect them or their offspring • Some disorders if caught early enough can be treated • PKU in newborns

  11. Gene Therapy • Gene Therapy: replacing defective genes with copies of healthy ones • First step is to isolate a copy of the gene • Next step is to transfer a healthy gene into the body and have it replace the defective gene

  12. Review • What is the difference between incomplete and codominance? • What are examples of some genetic disorders that are recessive? • Why would one utilize genetic counseling?

  13. Review- Answers • Incomplete dominance is when an individual displays a phenotype that is intermediate between two parents. Codominance is when two dominant alleles are expressed at the same time, both forms of character are displayed. • Examples of recessive genetic disorders are: sickle cell anemia, tay-sachs, cystic fibrosis, hemophilia A • One may utilize genetic counseling if they believe they or their offspring is at risk for a genetic disorder.

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