| First Author | Justice MJ | Year | 1988 |
| Journal | Mouse News Lett | Volume | 80 |
| Pages | 168-9 | Mgi Jnum | J:14276 |
| Mgi Id | MGI:62447 | Citation | Justice MJ, et al. (1988) New evidence supporting the allelism of T and tct. Mouse News Lett 80:168-9 |
| abstractText | Full text of MNL contribution: Research News: 1. New evidence supporting the allelism of T and tct. Additional data on the mapping of tctk (an ENU-induced allele of the t-complex tail interaction factor) relative to T (Brachyury), indicates that the two mutations map very close, rather than approximately 1 cM apart as reported in Justice and Bode (Gen Res 47: 187-192, 1986). We have observed a total of 1045 animals for recombination between T and tct, and find only the three recombinants previously reported (Bode, Genetics 108: 457-470, 1984). Unfortunately, these recombinants were not progeny tested. We observed the offspring from several different crosses for recombination between T and tct, the data for which are noted below. In each cross, a crossover between T and tct would yield 1) a T-tct double mutant which cannot be detected, or 2) a ++ animal which can be detected as a short-tailed mouse, and should carry flanking markers consistent with the genotypes of the parents. Mating: Female: T+qk/+tctk+ X Male: T+qk/+tctk+; Tail phenotype of offspring: Tailless: 76; Normal-tail: 39; Short-tail: 6; Qk and tf phenotype of possible recombinants: 1 short- tail quaking; 5 short- tail not qk. Mating: Female: T+qktf/+tctk++ X Male: T+qktf/+tctk++; Tail phenotype of offspring: Tailless: 209; Normal-tail: 128; Short tail: 1 1; Qk and tf phenotype of possible recombinants: 1 short- tail not qk, not tf. Mating: Female: T+tf/+tctk+ X Male: T+tf/+tctk+; Tail phenotype of offspring: Tailless: 329; Normal-tail: 191; Short-tail: 5; Qk and tf phenotype of possible recombinants: 2 short- tail, tufted; 3 short- tail, not tf. Mating: Female: T+qk+/+tctk+tf X Male: T+qk+/+tctk+tf; Tail phenotype of offspring: Tailless: 31; Normal-tail: 30; Short-tail: 0. Totals: Tailless: 645; Normal-tail: 388; Short-tail: 12; QK and tf phenotype of possible recombinants: Total 3 recombinants. Three short-tailed animals were classed as recombinants, but not progeny tested because of the low probability of obtaining an unusual short-tailed phenotype (of genotype T/tct) with an accompanying crossover between tct and qk (mating number 1) or between tct and tf (mating number three). These three probable recombinants were obtained early in the mapping crosses, and no other short-tailed quaking or tufted animals were observed, however 5 additional short-tailed animals that neither quaked nor were tufted were progeny tested and proved to be unusual phenotypes of the T/tct genotype. Because the three probable recombinants were not progeny tested, we cannot prove that they were in fact a result of crossing over between T and tct. We can state an upper limit of recombination between T and tct, however, assuming these three animals resulted from a crossover between the two markers. Thus, tct must map very close to T, certainly 0.4 cM or less. (Justice and Bode) Recombination between the two mutations was the basis for suggesting that the two genes were not alleles (Bode, Genetics 108: 457-470, 1984). An additional observation of one of us (Justice), leads one to believe that the genes are allelic. The induction of two T mutations in cis with tct allows an application of the classical genetic cis- trans test to these mutations. Briefly, when one of the mutations in consideration is dominant, if a different phenotype is seen in cis than in trans, the two mutations are considered to be part of the same functional unit or functionally related group of genes (Lewis, Cold Spring Harbor Sym on Quant Biol 16: 159-174, 1954). Two Brachyury mutations (Tkt1 and Tkt4) were induced by ethylnitrosourea in tw5 chromatin, which carries a resident tct gene as a part of the complete t-haplotype (Justice and Bode, Gen Res 47: 187-192, 1986). The tw5 chromosome in which they were induced gives tailless mice when trans with T. Both Tkt1 and Tkt4 have a dominant short- tailed phenotype. Therefore, T tct/+ + has a different phenotype than T +/+ tct, indicating that the two are functionally related, and thus either alleles or pseudoalleles. Three possibilities can explain these data: 1) the possible recombinant phenotypes observed resulted from crossovers between tct and tf, or between tct and qk, and had unusual tail phenotypes, but were not a result of crossover between T and tct, 2) rare crossovers occurred within the locus and were observed by us, indicating that the locus may be large or complex, or 3) the genes are pseudoalleles, functionally related but separable by recombination, also suggesting that the locus may be complex. (Justice) |
