High resolution RBA-banding comparison between early prometaphase chromosomes of cattle (Bos taurus L.) and goat (Capra hircus L.) at 700 band level.

High resolution RBA-banded early prometaphase chromosomes of cattle (Bos taurus L.) and goat (Capra hircus L.), from thymidine synchronized lymphocyte cultures, are compared at a level of 700 bands per haploid genome, with the purpose of detecting the extent of banding homologies between the two species and improving the resolution level of the ISCNDA (1989) standardized RBA-banded karyotypes. The results demonstrate that, at this level of resolution, at least 10 autosomes can be fully homologized between the two species, namely chromosomes 11, 16, 17, 18, 20, 21, 22, 23, 24 and 26, whereas the remaining autosomes show variations in some regions which require further investigations on more elongated chromosomes. Such investigations should also involve the use of GTG, GBG and RBG-banding techniques. These variations concern basically the relative distance of the bands from the centromeres or telomeres, appearance of subbands, and clustering of some positive bands.

Spontaneous rate of sister chromatid exchanges (SCEs) in mitotic chromosomes of sheep (Ovis aries L.) and comparison with cattle (Bos taurus L.), goat (Capra hircus L.) and river buffalo (Bubalus bubalis L.).

The spontaneous level of sister chromatid exchanges (SCEs) in the sheep, estimated by exposing peripheral blood lymphocytes in 0.1 microgram/ml of 5'-bromodeoxyuridine (BrdU), was 4.08 +/- 2.47 SCE/cell, 2.04 SCE/cell cycle, 0.038 SCE/chromosome. The dose-response relationships, observed by exposing the cells to 0.1, 0.25, 0.5, 1.0, 2.5, and 5.0 micrograms/ml of BrdU, rose rapidly from 0.1 to 0.25 microgram/ml, and less rapidly at higher concentrations, thus reaching a saturation level. The analysis of variance, performed on the square root transformed data at 0.1 and 5 micrograms/ml of BrdU, indicated significant differences (P < 0.001) among the four donors tested. The distribution of the SCE/cell frequencies in the cell population of the four donors followed the Poisson 'mixture' probability function, thus confirming previous findings. The spontaneous rate of SCE/cell of sheep is compared with those previously reported for cattle, goat and river buffalo. The theoretical and practical implications of the spontaneous sister chromatid exchanges are discussed in relation to their possible use in animal production for (a) better genetic evaluation of the breeding animals under selection, (b) more precise monitoring of the genotoxic effects of environmental pollutants.

Spontaneous rate of sister chromatid exchanges (SCEs) and BrdU dose-response relationships in mitotic chromosomes of goat (Capra hircus L.).

The spontaneous level of sister chromatid exchange (SCEs) in the goat, estimated by exposing peripheral blood lymphocytes to 0.1 microgram/ml of 5-bromodeoxyuridine (BrdU), was 3.28 +/- 1.71 SCE/cell, 1.64 SCE/cell generation and 0.027 SCE/chromosome. The dose-response curve of SCE/cell, observed by exposing the cells to 0.1, 0.25, 0.5, 1.0, 2.5, and 5.0 micrograms/ml of BrdU, rose rapidly from 0.1 to 0.5 microgram/ml, remained fairly stable from 0.5 to 1.0 microgram/ml and rose less rapidly from 1.0 to 5.0 micrograms/ml of BrdU. The frequency distribution of sister chromatid exchanges/cell and that of chromosomes showing various number of exchanges followed the Poisson probability at all BrdU levels; only at 5.0 micrograms/ml of BrdU was the fit found on the border of the 5% probability level. The usefulness of determining the spontaneous level of SCE/cell in domestic animals is discussed in relation to its possible application for a more precise evaluation of the genotoxic effects of environmental pollutants.

R-banding pattern of the prometaphase chromosomes of the goat.

R-banded prometaphase karyotypes of the goat are presented using both fluorescent and light staining techniques. A model for the standardization of the R-banded prometaphase goat karyotype is suggested.