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THE SCIENCE OF BIOLOGY 



Fig. 27. Chromosome Theory of Sex Determination and Explanation of Sex 

 Linked Heredity in Terms of Chromosomes. The number of chromosomes 

 is taken as 6 + 1 x in the male and 6 + 2 x in the female or 3n + 1 x and 

 3 n + 2 x when n = the number of pairs of non-sex chromosomes. The 

 chromosome, assumed to carry the determiner in a case of sex linked 

 heredity like color blindness in man, is partially shaded. See discussion in 

 text. Squares represent adult individuals, circles gametes (ova and 

 spermatozoa). 



