II. REPLICATION OF DNA IN CHROMOSOMES 



103 



3' LINKER 



Fig. 10. As each pair of chains begins repHcation, a new 3'R hnker is assumed to 

 be inserted which is resistant to the attack of the enzyme that opens the regular 

 3' Hnkers. When the pairs of chains finish rephcation their growing 3' ends are 

 assumed to be closed by the addition of another 3'R linker. The two new chromatids 

 would consist of these pairs of DNA molecules attached to a single axial element. 

 Another axial element (half-chromatid) would be added to each during the succeed- 

 ing late interphase or prophase. 



