l8 AN INTRODUCTION TO MODERN GENETICS 



FIG. PAGE 



24. Polyploid tomatoes 65 



25. Polyploid series in Crepis 65 



26. Polyploidy and cell size 66 



27. PoljT^loids in mosses 67 



28. Pairing in polyploids 69 



29. Metaphase association in polyploids 70 



30. Secondary polyploids 74 



31. Types of sex chromosomes 76 



32. Segregation of sex chromosomes 77 



33. Homologous and differential regions of sex chromosomes 78 



34. Sex linkage 80 



35. Secondary non-disjunction 81 



36. Chromosome complements in D. melanogaster 83 



37. Gynandromorphs and mosaics 86 



38. Plant chimaeras 87 



39. Cross-over maps of D. melanogaster 90 



40. Single and double crossing over 91 



41. Balanced lethals 93 



42. Environmental effects on crossing over 94 



43. Chromosome rearrangements 94 



44. Cytological and genetical evidence of a translocation 96 



45. Cross over and mitotic maps 97 



46. Maps of the X chromosome of D. melanogaster 99 



47. Pairing in chromosome rearrangements 100 



48. Two- and four-strand crossing over 102 



49. Crossing over and segregation 104 



50. Crossing over in triploids 106 



51. Types of Trisomies 108 



52. Segmental interchange and ring formation no 



53. Chromosome rings in Oenothera in 



54. Mitosis and meiosis 114 



55. Time of splitting of the chromosomes 117 



