Editorial Foreword 7
Acknowledgements 9
1．Inheritance：How We can Learn from Twins 11
2．Genes and Chromosomes 27
3．The Sex Chromosomes 46
4．Blood Groups and Plasma Proteins 53
5．Further Single-Factor Inheritance for Normal Human Variation -＇Tasting＇，Colourblindness，and Eye-colour 84
6．Height and Build 95
7．Intelligence 123
8．Gene Mutations：their Frequency and Effects 155
9．More about Gene Mutations 172
10．Chromosome Abnormalities in Man 194
11．Some Diseases amd Malformations due to Single Abnormal Mutant Genes 204
12．Some Common Illnesses for which there is Genetic Predisposition 216
13．Congenital Deformities 231
14．Looking to the Future - Eugenics 244
Suggestions for Further Reading 259
Index 261