Biology II

CHAPTER 14 OBJECTIVES

THE CHROMOSOMAL BASIS OF INHERITANCE

1. Explain how the observation of cytologists and geneticists provided the basis for the chromosome theory of inheritance.

2. Describe the contributions that Thomas Hunt Morgan, Walter Sutton and A.H. Sturtevant made to current understanding of chromosomal inheritance.

3. Explain why Drosphila melanogaster is a good experimental organism.

4. Define linkage and explain why linkage interfered with independent assortment.

5. Distinguish between parental and recombinant phenotypes.

6. Explain how crossing over can unlink genes.

7. Map a linear sequence of genes on a chromosome using given recombination frequencies from experimental crossses.

8. Explain what additional information cytological maps provide over crossover maps.

9. Distinguish between a heterogametic sex and a homogametic sex.

10. Describe sex determination in humans.

11. Describe the inheritance if a sex-linked gene such as color blindness.

12. Explain why a recessive sex-linked gene is always expressed in human males.

13. Explain how an organism compensates for the fact that some individuals have a double dosage of sex-linked genes while others have only one.

14. Distinguish among nondisjuction, aneuploidy and polyploidy; explain how these major chromosomal changes occur and describe the condequences.

15. Distinguish between trisomy and triploidy.

16. Distinguish among deletoins, duplications, translocations and inversions.

17. Describe the effects of alterations in chromosome structure, and explain the role of position effects in altering the phenotype.

18. Describe the type of chromosomal alterations implicated in the following human disorders: Down syndrome, Klinefelter syndrome, extra Y, triple-X syndrome, Turner syndrome, cri du chat syndrome and chronic myelogenous leukemia.

19. Define genomic imprinting and provide evidence to support this model.

20. Explain how the complex expression of a human genteic disorder, such as fragile-X syndrome, can be influenced by triplet repeats and genomic imprinting.

21. Give some exceptions to the chromosome theory of inheritance, and explain why cytoplasmic genes are not inherited in a Mendelian fashion.