Complex Traits

  1. Height in pea plants is monogenic/polygenic.

    2. Monogenic

  2. Height in humans is monogenic/polygenic.

    3. Polygenic (actually, multifactorial)

  3. What are polygenic traits? What are they characterized by?

    4. Polygenic traits are traits that are determined by more than two genes.

    They are characterized by continuous variation.

  4. What is continuous variation?

    5. A distribution of phenotypic characters that is distributed from one

    extreme to another in an overlapping, or continuous fashion.

    Continuous variation follows a normal curve.

  5. What is discontinuous variation?

    6. Phenotypes that fall into two distinct non-overlapping classes.

  6. What are complex traits?

    7. Traits that have an inherited component and that do not follow

    Mendel's laws.

     

  7. List and describe the two general types of complex traits.

    8. polygenic (quantitative) traits

    multifactorial traits = traits that result from the interaction

    of one or more environmental factors and two or more

    genes

  8. What are multifactorial traits?

    9. Traits that result from the interaction of one or more

    environmental factors and two or more genes

     

  9. List 10 examples of complex traits.

    10. Height in humans

    Cardiovascular disease

    Obesity

    Intelligence

    Schizophrenia

    Alcoholism

    Weight

    Neural tube defects

    Diabetes

    Hypertension

    Behavioral disorders

     

  10. What is empiric risk?

    11. A prediction of recurrence based

    on the trait's incidence in a specific

    population.

     

  11. Empiric risk increases with… .

    12. the severity of the disorder

    the number of affected family members

    how closely related a person is to the affected

    individuals

     

  12. What is heritability? What does it estimate?

    13. an expression of how much of the observed

    variation in a phenotype is due to differences

    in genotype.

     

  13. What is genetic variance?

    14. variation in phenotypic expression that results

    from different genotypes.

     

  14. What is environmental variance?

    15. Variation in phenotype between individuals of the

    same genotype.

     

  15. H = ____________ if the environment has no effect.

    16. 100%

     

  16. H = ____________ if all the phenotypic variation is due to the environment.

    17. 0%

     

  17. What is the coefficient of relationship?

    18. a statistic that measures the percentage of

    genes two related individuals have.

     

  18. What two types of people are especially useful in studying multifactorial traits?

    19. adopted individuals and twins

     

  19. Distinguish between monozygotic and dizygotic twins.

    20. Monozygotic (identical) twins result from a single fertilized ovum

    That splits. They have identical genes and are of the same sex.

    Dizygotic (fraternal) twins arise from two fertilized ova.

     

  20. What is concordance? What does it reflect?

agreement between traits exhibited by both members of

a twin pair.