394 



THE NEW INDIVIDUAL 



Part IV 



Distribution of chromosomes in the developmenrt of 

 sperm cells. Dork chromosomes = mole inheritance. 

 Light chromosomes = female inheritance. 



Body cell of fother _ 

 i.e. skin, muscle, etc. 



Germ cell destmed to divide 

 and develop into sperm cells 



Spermatogonium 



Primary — 

 spermatocyte 



MITOTIC 

 divisions 



Cell enlarges 



Similar chromosomes pair 



(Synapsis) 



Eacn chromosome duplicates 

 itself. Tetrads result. Tetrads 

 separate into pairs. Cell divides. 



MEIOSIS 



Tetrads separate into pairs. 

 Cell divides. 



A.B.MEIOTIC 

 divisions 



Secondary 

 spermatocyte - 



Sister chromosomes 

 separate. 



Spermatids 



Sperm 

 cells 



Fig. 20.5. The reduction (meiosis) of the number of chromosomes from the 

 double (diploid) to the single (haploid) number during the formation of sperm. 

 For each sex cell, the process includes: increase in number of cells by MITOSIS; 

 reduction of chromosomes by MEIOSIS. For simplicity, six chromosomes are used 

 in the body cells. Cells of the human body contain 48 chromosomes. 



