It was shown that sz and J are closely linked and that the recombination frequency between these two genes is 7.41 +/- 2.91. It was also shown that J is not linked with markers in linkage groups I and III, and that sz is not linked with a marker in linkage group II. Therefore, linkage between sz and J is a new linkage group. Since only three linkage groups have so far been established in the Syrian hamster, linkage groups I, II and III, this new linkage constitutes linkage group IV.
