III. BACTKRIOFHAliE UNA AND BACT?:K1AL UNA 



115 



characteristic of DNA. In an effort to rule out the l)os;^ibility that these 

 reflections came from extra-particular DNA, they studied the 24 A 

 equatorial spacing as a function of relative humidity. Their results 

 show that the fibers containing phage do not show the continuous in- 



1000 3000 5000 



SHEAR (sec-) 



7000 



Fig. 1. The birefringence of phage particles and ghosts. This figure shows the 

 way in which the birefringence (mole"^ Uter"') changes as a function of shear gradient 

 for intact T4 phage (lower curve) and phage ghosts (upper curve). If the DXA were 

 completely randomized within the phage head, the birefringence of intact phage 

 would be expected to superimpose approximately with that of the ghosts. (From 

 Gellert, 1962.) 



crease in this side-to-side packing distance as the relative humidity 

 approached 100%. With fibers of purified DNA this spacing increases 

 indefinitely as the fiber dissolves. In this regard, the fibers containing 

 phage are similar to DNA-protamine complexes. At present it is not 



