182 



CELL HEREDITY 



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FIGURE 7.1. Lampbrush chromosomes of amphibian oocytes (from J. G. Gall, 1958, 

 in: The Chemical Basis of Development, Baltimore, The Johns Hopkins Press, pp. 

 103-135). 



(o). A very diagrammatic representation of a lampbrush chromosome showing 

 the homologues held together at two chiasmata. Hundreds of loop pairs extend 

 laterally from the axis of each homologous strand. 



(fa). A somewhat schematic view of a lampbrush chromosome to show the central 

 axis of the chromomere, a very delicate strand (usually invisible with the light micro- 

 scope). Loop pairs of diflfering morphology project laterally from the axis. The loops 

 are more closely spaced on the actual chromosome. 



(c). Diagram of the postulated structure of a lampbrush chromosome based upon 

 electron microscope studies and enzyme digestion. 



diagram interpreting its structure on the basis of enzymatic and electron 

 microscope investigations. The chromomeres are postulated to be highly 

 condensed coils of the pair of chromosomes which make up the double 

 continuous fiber running through both the axis and the loops, one 

 chromosome on each side. (The homologous chromosomes are paired, 

 this being meiotic prophase.) Measured at its narrowest point, in the 

 fine strand between chromomeres, the chromosome is only 100-200 A 

 in diameter. 



Most chromosomes do not provide material for structural analysis com- 

 parable with the lampbrush chromosomes of amphibian oocytes. None- 



