Chap. 3 



LIVING MATTER AND CELLS 



45 



Distribution of chromosomes m the development of 

 egg cells. Light chromosomes = female inheritance. 

 Dark chromosomes = mole inheritance. 



MITOTIC 

 divisions 



Body cell of mother I.e. 

 skin, muscle, etc. 



Germ cell destined to divide 

 and develop into eggs. 



Oogonium 



Fertilization 



Cell enlarges 



Similar chromosomes pair 



(Synapsis) 



Each chromosome duplicates 

 itself. Tetrads result. 

 Tetrads separate into pairs 



A.B. MEIOTIC divisions 



Cell divides, 3 pairs of 

 chromosomes in each 



Cell divides 

 3 chromosomes 



./a V 



Mature 

 egg 



Second polar body 



B 



Primory 

 Oocyte 



Primary 

 Oocyte 



Secondary 

 Oocyte 



First 

 polar body 



These cells 

 die 



an increase in number of chromosomes by MITOSIS and a reduction in the number 

 of chromosomes by MEIOSIS. For simphcity six chromosomes are used here for 

 body cells. Cells of the human body have 48 chromosomes. 



