Changes Involving Unbroken Chromosomes 163 



1 1.7. Discuss the statement: All somatic cells from diploid zygotes are chromosom- 

 ally identical. 



I 1.8. Do you suppose that the human species will henefit from a discovery that certain 

 of its members are trisomic? Explain. 



1 1 .9. What are the advantages of allopolyploidy? Of allopolyploidy? 



11.10. What genetic explanation can you offer for the fact, demonstrated in Figure 

 1 1-2. that the seed capsule of the Datura haploid is smaller than that of the 

 triploid? 



1.11. What do you consider to be the advantages and disadvantages of polynemy? 



1.12. Unfertilized mammalian eggs can contain ploidies of IN. 2N. 3N, or 4N. 

 Explain how each of these could be produced. 



1.13. How can you explain the fact that persons with Down's syndrome are more 

 susceptible to leukemia than normal diploids? 



1.14. Explain why individuals with Down's syndrome show a wide variety of pheno- 

 typic differences as well as similarities in their abnormalities. 



1.15. Some babies classified as normal at birth are clearly mongoloid when a year 

 old. What would you do to assure an early diagnosis of Down's syndrome? 



1.16. Would you expect a correlation between producing a child with Down's syn- 

 drome and the frequency with which the mother has abortions? Subsequent 

 children with Down's syndrome? Explain. 



1.17. Should a woman with a trisomic mongoloid sibling be more than ordinarily con- 

 cerned about having a child of this type? Explain. 



1.18. After examining Figures 11-8 and 11-9, discuss the precision with which a 

 given human chromosome can be identified. 



1.19. How would you proceed to determine the somatic chromosome composition 

 of a given human individual? 



1.20. Discuss the phenotypic effects of adding an N-l genome to individuals that are 

 normally N. 2N, 3N. or 4N. 



1.21. R. A. Turpin reported two cases of monozygotic twins. One set contains an 

 XY male and an XO female; the other set is composed of a disomic-21 male 

 and a trisomic-21 male. Discuss the mechanisms probably involved in pro- 

 ducing such twins. Include in your hypothesis the additional fact that one XO 

 cell is also found in the first XY individual mentioned. 



