Lecture 32: Genetic Fine Structure: Tetrad Analysis, Complementation, Cistrons
1. Briefly describe two experimental systems in which all of the products of a single meiosis can be recovered. How are such systems used in genetic analysis?
2. Explain how the centromere is used as a genetic marker when analyzing patterns of crossing over in Neurospora
3. What are the major differences in life cycles between the two types of yeast that are widely used in genetic research?
4. What is meant by the term "tetrad" and why is tetrad analysis of importance in genetic research?
5. Distinguish between ordered and unordered ascospores and explain how each can be used in genetic research.
6. Explain how a single crossover can generate either a 2:2:2:2 pattern or a 2:4:2 pattern in the ascospores of Neurospora.
7. Briefly describe the life cycle of Saccharomyces cerevisiae and explain how it can be used for tetrad analysis.
8. Why is a tetratype with four different types of spores a more common occurence than a non-parental ditype, which has only two different types of spores?
9. What are the advantages of doing tetrad analysis with Neurospora ? What are the limitations of such studies?
10. What special values does tetrad analysis bring to genetics. What can be done with it that cannot readily be done with Drosophila or peas?
11. Describe the process of formation of a plaque by bacteriophage.
12. How is genetic linkage studied in bacteriophage?
13. What properties make bacteriophage such a powerful tool for recombinational analysis?
14. Describe the phenomenon of complementation as it occurs among various rII mutations in bacteriophage T4.
15. Explain why complementation studies cannot be done with dominant mutaitons.
16. Bacteriophage mutations A and B do not complement each other when tested in a recombination-deficient strain of bacteria. However in strains that support recombination, there is occasional restoration of function. Explain how this can happen. (You will need to do some reasonable extrapolation beyond what has actually been presented to answer this.)
17. How can complementation studies be done in various types of organisms that normally have only a single haploid genome. (You should be able to come up with several examples from different organisms).
18. What is meant by the term cistron? What is the origin of the term?
19. Does complementation between two mutant strains prove that both mutations have occurred within the same biochemical pathway? Explain your answer, including any restrictions you have placed on definitions of terms that you use.
20. How can you distinguish whether restoration of function by coinfection with two mutant bacteriophage is due to complentation or recombination?
21. What would you do to analyze the frequency of recombination between two mutant strains of bacteriophage that complement each other? (This calls for some projection beyond what has been covered in class, but should be possible to answer based on what you have been told about complementation and about recombination).
22. Cite an example of complementation in a diploid organism. What F2 phenotypic ratio is expected when mutant strains that exhibit complementation are crossed?
23. Can recombination occur within the coding unit for a single protein? Cite evidence to justify your answer.
24. Can complementation occur within the coding unit for a single protein? Cite evidence to justify your answer.
25. Explain how deletion mapping can be used for preliminary placement of previously unstudied mutations within a particular portion of a cistron.
26. Briefly summarize the process of gene conversion, including how the Holliday model of genetic recombination explains its occurence.
27. Briefly describe each of the following, including where it is likely to be observed:
a. Sister chromatid exchange
b. Mitotic crossover
c. Complementary gene action
d. Complementation
e. Non-parental ditype
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