Genetics 297 



is never exactly like them. Thus stability in inheritance goes hand in 

 hand with variations. 



The scientific study of the inheritance of characters from genera- 

 tion to generation is known as genetics. The resemblance of indi- 

 viduals of common descent is known as heredity. More precisely ge- 

 netics attempts to discover the laws which control not only the resem- 

 blances but the variations that occur. 



At present it is known that the gap from generation to generation 

 is bridged by the gametes. It is in the egg and sperm that the mate- 

 rials are located w^hich will give rise to the new generation with its 

 resemblances and variations. This fact was clearly stated by Weismann 

 in his theory of the continuity of the germplasm. The beginnings of a 

 scientific understanding of heredity were impossible until the true 

 nature and meaning of sexuality in both plants and animals w^ere recog- 

 nized. Some of the early microscopists made this important contri- 

 bution in the seventeenth and eighteenth centuries. 



The founder of modern genetics was Mendel, an Austrian monk. 

 Working in his monastery garden, he observed that certain variations 

 existed among the pea plants which he was tending. The plants varied 

 in height, in the color of the flowers, and in the nature of the seed 

 produced. No doubt these variations had been noted before, but until 

 Mendel no one had carefully observed and studied them. He kept care- 

 ful records of his plants and thus knew the ancestry of each individual 

 plant. He cross-fertilized them and then studied specific characters. 

 He kept accurate count of the individuals showing certain specific char- 

 acters. In this way, he showed that inheritance was not a random affair, 

 but rather was subject to definite laws. He demonstrated that the 

 traits of the offspring were predictable if those of the parents were 

 sufficiently well understood. 



Unfortunately Mendel's work which he published in 1866 was lost 

 to the scientific world for over thirty years. With the discovery of 

 this w^ork in the early 1900's, the science of genetics had its beginning. 

 Since then, it has grown into a science which influences all of our 

 lives and has contributed much to human well-being. With this dis- 

 covery of his work, the laws which he formulated became the basis of 

 our present knowledge. 



