Genetics has been progressing apace. Gene therapy which was earlier a mere thought is now practiced with reasonable success. The excitement and fascination human genetics has generated in the recent past has broadened the horizon beyond limits. But it has also overburdened medical undergraduates. Therefore only the most essential details have been included in this edition; superfluous text has been omitted. All the chapters have been revised and updated. The line drawings have been redrawn neatly. Two new chapters namely `Developmental Genetics` and `Gene Therapy` have been added.