Lecture 34: Chromosomal Changes, Monosomy, Trisomy, Polyploidy, Structural Changes
1. Distinguish between the following pairs in a manner that makes it clear that you know what each is and how they differ.
a. Euploid and aneuploid
b. Triploidy and trisomy
c. Autopolyploid and allopolyploid
d. Hybrid and allopolyploid.
e. Diploid and amphidiploid
f. Homologous and homeologous.
2. Why are allotetraploids more likely to be fully fertile than autotetraploids?
3. Describe a process for the experimental generation of an allotetraploid from a cross-species hybrid.
4. Does the chromosome number of an allotetraploid have to be an even multiple of four? Explain your answer.
5. What is the agricultural significance of allopolyploids? (You should be able to think of more than one answer).
6. Describe two distinctly different reasons why triploid plants may be preferred for certain agricultural crops.
7. A fertile allopolyploid plant with a chromosome number of 38 is crossed with one of its parent species. Do you expect the progeny to be fertile? Explain your answer.
8. Does the formation of an allotetraploid between two plant species insure that the most desirable properties of both will be found in the allotetraploid? Explain the reasoning behind your answer.
9. What approach would you use to attempt to construct an allotetraploid from two plant species that are not capable of cross pollination? Describe the steps that are involved.
10. How does a diploid banana differ from commercially sold bananas?
11. What problems stand in the way of fertility of triploid plants?
12. What features make polytene chromosomes particularly useful for the detection of altered chromosomal structure?
13. Where other than a polytene chromosome could one look to verify the existence of a chromosomal inversion or partial duplication?
14. Define the following terms
a. Dicentric chromosome
b. Tandem duplication
c. Pseudodominance
d. Paracentric inversion
e. Unequal crossing over.
15. Deletions, duplications and inversions all cause the formation of loops in polytene chromosomes. How would you distinguish among these three possibilities cytologically? What genetic traits would you look for to support your conclusions?
16. Describe the mechanisms that lead to the production of Doublebar progeny from crosses of males that are hemizygous for Bar eye with females that are homozygous for Bar eye.
17. An inversion loop is more likely to cause severe problems during meiosis than a deletion loop. Explain the difference.
18. Under what conditions is a duplication of genetic material not abnormal?
19. What special property distinguishes a deletion mutation from a typical missense point mutation (one that codes for the wrong amino acid)?
20. Explain how a deletion mutation can cause partial hemizygosity.
21. What type of chromosomal change is particularly likely to result in a dominant phenotype with lethality in the homozygous state. What mechanism is likely to be involved in the lethality.
22. Are all seedless fruits triploid? Explain your answer.
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