Chap. 20 



THE PHYSICAL BASIS OF HEREDITY 



409 



Fig. 20.17. Patterns of hereditary baldness. The gene for baldness is inherited 

 by men and women but has different results. The most convincing theory is that 

 difference in hormones acting on the same kind of gene may be responsible for the 

 baldness in men and the usual lack of baldness in women. (Courtesy, Snyder: 

 Principles of Heredity, ed. 4. Boston, D. C. Heath and Co., 1951.) 



Fig. 20.18. A mutation for short legs in sheep; short-legged ewe in the center, 

 ordinary sized sheep of the same variety at left and right. 



In 1791, a Massachusetts farmer found in his flock a short-legged lamb from 

 which he bred a strain of sheep, valuable to him because they did not jump the 

 pasture walls. This variety, called Ancon sheep, still exists. (Photograph from Life 

 Magazine © Time, Inc. Courtesy, Storrs Agricultural Experiment Station.) 



