Genetic and cytogenetic marking of the neurological quaking mutation (qk) in laboratory mice

A new genetically balanced breeding system with a low recombination rate is offered for purposes of maintenance and early identification of mice with the recessive autosomal qk mutation. Dominant T mutation (Brachyury) and recessive t12 mutation of T locus were chosen as genetical markers and Robertsonian translocation Rb (8.17) 1 Iem served as a cytogenetical marker of the qk mutation. As shown by the results, none of genetical mutations studied (qk, T or t12) can be distinguished on differentially stained chromosomal preparations. Hybrid mice of the +T/qk+ genetic compound have a high rate (44%) of homozygous qk/qk offspring. The latter can be identified with the high probability (96%) in foetuses and newborns, according to their tail length, well before the typical neurological symptoms are evident. In the offspring of the F1 hybrids+Rb 1 Iem/qk+ the frequency of qk/qk mice is near 20% and they can be identified with the probability 95% at any stage of the development by means of chromosomal analysis. Hybrids of the +t12/qk genotype are very convenient for prolonged maintenance of the qk gene in a balanced heterozygous condition. Some features of functional similarities between the qk gene and recessive mutations of T locus are discussed. Genetical and cytogenetical markers used in this work provide some novel approaches for experimental analysis of the qk gene expression at early stages of the development.