Download SI Worksheet #16 (Chapter 15) BY 123 Meeting 11/4/2015 Chapter

SI Worksheet #16 (Chapter 15)
BY 123
Meeting 11/4/2015
Chapter 15: The Chromosomal Basis of Inheritance
1. What does the chromosome theory of inheritance state about the way genes are inherited?
2. What are the 4 characteristics of Thomas Hunt Morgan’s Drosophila melanogaster (fruit
flies) that made them “model organisms?”
3. What is the phenotype for a character most commonly observed in natural populations
called? How do you represent these?
4. What is the name given to traits that are alternative to the wild type? How are they
represented?
5. Draw the Punnett Square of Morgan’s experiment on eye color, a cross between a wild-
type female fruit fly and a mutant type male.
a. What color eyes will the F1 offspring have?
b. Is the white eye trait recessive or dominant to the red eye trait? How do you know
this?
c. What color eyes will the F2 offspring have? What sex has white eyes?
d. What can we conclude about the location of the eye-color gene on the
chromosome?
6. What is a sex-linked gene?
7. Is it possible for a female to exhibit the phenotype for an X-linked recessive gene? If so,
what cross would lead to this phenomena? (Hint: Draw the cross using Morgan’s fruit
flies eye color)
8. Discuss the difference and similarities between the sex chromosomes in the X and Y
classification system.
9. Are there more X-linked genes or Y-linked genes? Why?
10. What is the SRY? In the absence of this region, what develops?
11. What is a Barr body?
12. Why can only female cats be termed calico (have patches of orange and black fur)?
13. Discuss the four different systems of sex determination outlined in your book.
14. What are linked genes?
15. What phenotype(s) were present in the F1 generation in Morgan’s dihybrid cross on wing
type and body size? What phenotype(s) were present in the F2 generation?
16. What accounts for the recombination of linked genes?
17. What is a linkage map?
18. What is nondisjunction?
a. If nondisjunction occurs in meiosis I, what are the resulting number of
chromosomes in the gametes?
b. If nondisjunction occurs in meiosis II, what are the resulting number of
chromosomes in the gametes?