Gene Mutations 



227 



newly appearing, inherited types are the result of actual changes 

 in the genes themselves and are known as gene mutations. 



Although these three types have all frequently been classed 

 as mutations, since they all appear suddenly and are inherited, 

 the word mutation has more recently been used largely in the 



Fig. 72, A double-flowered Oenothera; mutant supplena of Shull, a 

 homozygous recessive tj'pe. (Courtesy of Dr. G. H. Shull.) 



restricted sense of gene mutations. Throughout this book, how- 

 ever, it is used for all inheritable changes unless preceded by a 

 qualifying adjective. 



Gene Mutations 



A gene mutation is the result of a change in the structure of 

 an individual gene. It is also known as a point mutation, since 

 it involves a change at only one point or locus in the chromo- 

 somes of the organism. 



Gene mutation is one of the most important if not the most 

 important factor in the origin of new species. Other factors 

 are also involved in speciation, but gene mutations provide the 



