| First Author | Cattanach BM | Year | 1982 |
| Journal | Mouse News Lett | Volume | 66 |
| Pages | 62-3 | Mgi Jnum | J:22907 |
| Mgi Id | MGI:71498 | Citation | Cattanach BM (1982) Non-disjunction tests with Robertsonian translocations. Mouse News Lett 66:62-3 |
| abstractText | Full text of MNL contribution: 2. Non-disjunction tests with Robertsonian translocations. a) as determined by frequency of zygotic deaths. Previous tests with 3 metacentric chromosomes of tobacco mouse origin (RblBnr, Rb4Bnr, Rb6Bnr) have shown that each causes high levels of non-disjunction when heterozygous with the homologous house mouse acrocentrics even after 10 or more generations of' backcrossing to house mouse stocks (Cattanach, MNL 61: 38; Cattanach and Jones, MNL 62: 50). Similar findings have now been obtained with 2 further such metacentrics, Rb2Bnr and Rb3Bnr. As found before, the non-disjunction levels may in some cases be higher than originally observed in equivalent studies upon mice on a mixed tobacco mouse - house mouse genetic background (Cattanach and Moseley, Cytogenet. Cell Genet. 12: 264-287, 1973). However, this may only be due to small sample size and a heterogeneity between animals. Metacentrics of laboratory mouse origin typically do not cause high levels of non-disjunction. However, Gropp and Winking (Biol. of the House Mouse, 1981) have recently reported that metacentrics of feral mice origin may give lower levels of non-disjunction when heterozygous in the original wild genome. Laboratory mouse metacentrics might therefore give elevated non-disjunction levels after crossing to such acrocentric chromosome feral mice. Feral mice other than those of the Peru-Coppock (Margaret Wallace) strain are not maintained at Harwell but tests with the laboratory mouse metacentric Rb2Ct after crossing to Peru-Coppock have failed to demonstrate increased non-disjunction levels when compared with both concurrent and earlier data (MNL 61: 50). Discordance between repeat experiments was the principle finding. Some evidence that Rb2Ct gives high levels of non-disjunction in heterozygous females was found. The results were as follows: Rb2Bnr/+ (original data): Pre-impl. Loss: 4.7%; Post-impl. Loss: 17.7%; Total loss: 21.7%; Rb2Bnr/+: Pre-impl. Loss: 29.9%; Post-impl. Loss: 22.7%; Total loss: 41.2%; b Rb2Bnr wa-1/+++; Pre-imp. Loss: 14.3%; Post-impl. Loss: 34.7%; Total loss: 44.0%; Rb3Bnr/+ (original data): Pre-impl. Loss: 7.7%; Post-impl. Loss: 20.3%; Total loss: 26.5%; Rb3Bnr/+: Pre-impl. Loss: -3.8%; Post-impl. Loss: 16.2%; Total loss: 12.9%; Bf Rb3Bnr bt/+++: Pre-impl. Loss: 5.6%; Post-impl. Loss: 14.2%; Total loss: 19.0%; Rb2Ct/+ males (earlier data): Pre-impl. Loss: 1.5%; Post-impl. Loss: 2.7%; Total loss: 4.1%; Rb2Ct/+ males (Peru-Coppock): Pre-impl. Loss: 1.5%; Post-impl. Loss: 3.2%; Total loss: 4.6%; Rb2Ct/+ males (Control): Pre-impl. Loss: 4.3%; Post-impl. Loss: 6.6%; Total loss: 10.5%; Rb2Ct/+ females (Peru-Coppock): Pre-impl. Loss: -3.3%; Post-impl. Loss: 2.2%; Total loss: -0.9%; Rb2Ct/+ females (control): Pre-impl. Loss: 7.8%; Post-impl. Loss: 7.5%; Total loss: 15.9%. b) as determined by gene marker methods. Non-disjunction tests using a gene marker method (Lyon, Simpson and Ward; Cattanach and Moseley, MNL 51: 20-21) have previously been carried out with heterozygotes for individual tobacco mouse metacentrics (Cattanach, Murray and Tracey, MNL 54: 37). The animals were of a mixed tobacco mouse - house mouse genetic background. The results were in partial agreement with estimates of non-disjunction obtained by other methods. Discordant and variable results were attributed to genetic background effects. RblBnr, Rb2Bnr and Rb3Bnr, now established on a house mouse genetic background, have been reinvestigated. The results suggest different non-disjunction levels for the different metacentrics and also for the various chromosome arms. Reciprocal cross differences were found and could result from genetic background differences. Maternal age effects were also important. However variability between repeat experiments was a main feature of the data. Since variability is also found with other methods, heterogeneity between animals would appear to be the cause. A modified gene marker method has also been investigated. This tested heterozygous RblBnr males against tester females doubly heterozygous for RblBnr and Rb2Ct which because of the monobrachial homology between the 2 metacentrics, should have high levels of non-disjunction for chromosome 1. The results differed according to whether the females or males were marked, further demonstrating the problems associated with investigating non-disjunction caused by Robertsonian translocations. The reciprocal crosses could not be carried out with this form of test due to the sterility of the males doubly heterozygous for the two metacentrics. An outline of the results is as follows with RblBnr shown as R1B, Rb2Bnr as R2B, Rb3Bnr as R3B, and Rb2Ct as R2C: Cross: R1B+/++ female x R1Bln/+ln male (original data); No. progeny scored: 1156; % with gene marker: 2.42% ln; Cross: RIB+/++ female x RlBln/+ln male; No. progeny scored: 512; % with gene marker: 1.37% ln; Cross: repeat; No. progeny scored: 540; % with gene marker: 0.19% ln; Cross: RlBln/+ln female x RIB+/++ male; No. progeny scored: 631; % with gene marker: 1.74% ln; Cross: repeat; No. progeny scored: 589; % with gene marker: 2.04% ln; Cross: +R2B/++ female x bR2B/b+ male; No. progeny scored: 733; % with gene marker: 2.05% b; Cross: +R2B/++ female x mR2B/m+ male; No. progeny scored: 921; % with gene marker: 0.43% m; Cross: R2B+/++ female x R2Bwa-l/+wa-1 male (original data); No. progeny scored: 698; % with gene marker: 1.15% wa-1; Cross: +R2B+/+++ female x bR2Bwa-l/b+wa-1 male; No. progeny scored: 481; % with gene marker: 1.03% b; 0.62% wa-1; Cross: repeat; No. progeny scored: 537; % with gene marker: 1.02% b; 0% wa-1; Cross: bR2Bwa-l/b+wa-1 female x +R2B+/+++ male; No. progeny scored: 411; % with gene marker: 1.01% b; 0% wa-1; Cross: repeat; No. progeny scored: 632; % with gene marker: 2.22% b; 1.11% wa-1; Cross: + R3B/++ female x bfR3B/bf+ male; No. progeny scored: 1090; % with gene marker: 0.46%; Cross: R3B+/++ female x R3Bbt/+bt male (original data); No. progeny scored: 1321; % with gene marker: 0.61%*; Cross: +R3B+/+++ female x bfR3Bbt/b£+bt male; No. progeny scored: 654; % with gene marker: 1.38% bf; 1.07% bt; Cross: repeat; No. progeny scored: 522; % with gene marker: 2.29% bf; 0.38% bt; Cross: bfR3Bbt/bf+bt female x +R3B+/+++ male; No. progeny scored: 580; % with gene marker: 0.52% bf; 0.52% bt; Cross: repeat; No. progeny scored: 380; % with gene marker: 0.53% bf; 0.26% bt; Cross: RlB+/R2C+ female x RlBln/+ln male; No. progeny scored: 335; % with gene marker: 4.78% ln; Cross: RlBln/R2Cln female x RIB+/++ male; No. progeny scored: 457; % with gene marker: 1.97% ln. * with misclassification problems (Cattanach) |
