| First Author | Dunn LC | Year | 1966 |
| Journal | Mouse News Lett | Volume | 34 |
| Pages | 21-22 | Mgi Jnum | J:15057 |
| Mgi Id | MGI:63200 | Citation | Dunn LC (1966) Linkage: T and tf on Chr 17. Mouse News Lett 34:21-22 |
| abstractText | Full text of MNL contribution: A new recombination test between T (Brachury) and tf has been carried out with the following result: Male: T-tf/++; Female: +tf/+tf; normal: 136; Brachy tufted: 138; normal tufted: 15; Brachy non tf: 11; Male: T+/+tf; Female: +tf/+tf; normal: 7; Brachy tufted: 11; normal tufted: 150; Brachy non tf: 134; Male: +tf/+tf; Female: T-tf/++; normal: 160; Brachy tufted: 158; normal tufted: 15; Brachy non tf: 13; Male: +tf/+tf; Female: T+/+tf; normal: 2; Brachy tufted: 5; normal tufted: 20; Brachy non tf: 16; This leads to recombination fractions: Male 44/602=7.31%+/-1.06; Female 35/389=9..00+/-1.45 This is in good agreement with Lyon '64: Male 30/496=6.02+/-1.05; Female 46/499=9.22+/-1.30 We propose to use as standard recombination fraction for this interval: Male 74/1098=6.74+/-.76; Female 81/888=9.12+/-.97 The fertility of 19 males of our Brachy tufted stock has been estimated in rnatings with fertile females of the same stock. In a total of 195 "mating units" (l95 periods of four weeks) 739 offspring were sired, a mean of 3.8 per mating unit with a range for different males 2.4-4.7. This is taken as "normal" fertility under our conditions. Two viable alleles derived from different wild populations tw8 (Virginia) and tw36 (Arizona) have been compared with respect to their interactions with a standard lethal allele, to. Males homozygous for tw8 or tw36 are entirely sterile. Compound males tw8/to and tw36/to are also sterile. The proportions of viable normal tailed offspring at birth were compared with the proportions expected assuming full viability of homozygotes and compounds and male transmission ratios: tW36=.99; tw8=.8; to=. 8. The results were: Parents: Male: T/tw8 x T/tw8 Female; Offspring - tailless (T/t): 947; normal tail (t/t): 124; Proportion normal exp.: .444; Proportion observed: .120; % obs x 100 exp.: 27.3; Parents: Male T/tw8 x T/to Female; Offsrping - tailless: 433; normal tail: 24; Proportion normal exp.: .444; Proportion observed: .053; % obs x 100 exp.: 11.9; Parents: T/tw36 x T/tw36; Offspring - tailless: 493; normal tail: 105; Proportion normal exp.: .495; Proportion observed: .175; % obs x 100 exp.: 35.5; Parents: T/tw36 x T/to; Offspring - tailless: 319; normal tail: 27; Proportion normal exp.: .444; Proportion observed: .078; % obs x 100 exp.: 17.6; Parents: T/to x T/tw36; Offspring - tailless: 175; normal tail: 13; Proportion normal exp.: .495; Proportion observed: .073; % obs x 100 exp.: 14.8; The percentages in the last column above are estimates of the relative viabilities of the homozygotes and compounds. It is evident that neither "viable" allele when homozygous attains more than about a third of the expected or normal viability at birth. Substitution of a to (lethal) allele for one of the viable alleles reduces the viability of the compound to about one-half that of the "viable" homozygote (27% to 12% and 35% to 15-17%). The similarity of the two "viable" alleles in their interaction with a third allele both in male sterility and in viability effects is taken to indicate that tw8 and tw36 may represent the same allele. Differences in male transmission ratios of these alleles in different populations remain to be explained. A sample of 43 males and 8 females (born in October 1964) from the Rockefeller wild stock (Schneider) was tested by crossing with Brachy during 1965. Of these 24 were shown to be +/+ and 27 were +/tw, the t-allele being presumably tw2 known to be present in this stock. This corresponds to a minimum t-allele frequency of about .36 as compared with .38 in 1963 and .37 in 1955-59. The male transmission ratio of t in the 1965 sample was estimated as .915 as compared with .9 in 1963. These values have thus been stable in this closed stock for some 12 years. |
