Sex Determination 115 



8.25. A white cat reported by H. C. Thurline, had one yellow and one blue eye, a 

 phallus and one testis, one uterine horn, and one ovary. Although the animal 

 had 38 chromosomes (the normal diploid number), some nuclei had an XX 

 and others, an XY content. Suggest hypotheses to explain the chromosomal 

 content of this individual. 



8.26. Give a possible chromosomal formula for human individuals who are: 



(a) Triploid males 



(b) Klinefelter's type of male 



8.27. A 26-year-old somewhat mentally retarded man is known to be XYY but other- 

 wise diploid. To what do you attribute the apparent rarity of this type of 

 chromosomal constitution? 



8.28. Klinefelter-type males occur who are XXXYY. Give a possible origin of this 

 chromosomal constitution. 



8.29. In the insect Protenor and certain short-horned grasshoppers, all eggs have the 

 same number of chromosomes, and half of the sperm are different, in that they 

 carry one less chromosome. What is the cytogenetic basis for sex determination 

 in such cases? 



8.30. In the plant genus, Melandrium, one observes individuals of the following types: 

 Diploid: XX + 11AA-5 XY + 1 1 AA = 6 



Triploid: XXX + 1 1 AAA = 9 XXY + 1 1 AAA = <$ 



Tetraploid: XXXX + 1 1 A AAA = $ XX YY + 1 1 AAAA = $ 



or 

 XXXY + 1 1 AAAA = $ 

 Discuss the cytogenetic basis for sex determination in Melandrium. 



8.31. Discuss the sex ratio expected in the honey bee from unmated and mated females. 



8.32. Does the chromosomal balance hypothesis of sex determination apply in the 

 case of parasitic wasps? Explain. 



8.33. Compare the self-sterility alleles in Nicotiana (see p. 60) with the sex-determination 

 alleles in Habrobracon. 



