CHAPTER IV 

 MENDEL'S LAW 



Mendel's law is the basis of all work in genetics and 

 should be understood from its original statement to its 

 somewhat complex development. Before passing to the 

 more complex features it is well to recall the points of 

 the original thesis. 



In 1865 GREGOR MENDEL (2) published in the pro- 

 ceedings of a local scientific society the result of eight 

 years of breeding experiments. The publication was so 

 obscure that scientific men in general did not see it, and, 

 in addition t6 this, Darwinism was at that time absorbing 

 the attention of biologists. For these two reasons 

 MENDEL'S work remained unnoticed, and of course 

 unappreciated, until it was discovered in 1900 and 

 became the great classic of genetics. Its influence, 

 therefore, dates from 1900 rather than from the year of 

 its publication. 



The substance of MENDEL'S experiments is as fol- 

 lows. Wishing to discover the contributions of each 

 parent to the make-up of their progeny he chose for his 

 work the simple garden pea, which would breed rapidly, 

 and exhibited well marked varieties. To magnify his 

 results he secured hybrids by crossing distinctly different 

 types of peas, and to avoid confusion he considered 

 only one character in each experiment. For example, 

 he crossed peas which contrasted in character of height, 

 of flower color, and of seeds. In every case he obtained 



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