Physical gene mapping by in situ hybridization is a difficult task in an 
all-acrocentric mouse karyotype, because all of the chromosomes are 
morphologically very similar. These difficulties can be overcome by using the 
many different metacentric Robertsonian translocation (Rb) chromosomes derived 
from wild mice. Here we describe the establishment of two Moloney murine 
leukemia virus-transformed suspension cell lines, WMP-1 and WMP-2, derived from 
wild mice of the strain WMP/WMP. These mice carry nine pairs of metacentric Rb 
chromosomes containing chromosomes 1 to 18. Chromosome 19 and the sex 
chromosomes are the only acrocentric chromosomes. Furthermore, a heterozygous 
reciprocal translocation between chromosomes 13 and 17 involved in two Rb 
chromosomes is present in this stock and provides additional marker chromosomes. 
The chromosome designation of these mice is Rb(10.17)9Mpl Rb(13.15)10Mpl 
T(13.17)1Lub.