D. Matassino

Cytogenetic observations on a Robertsonian translocation in Saanen goats

The RBA banding pattern demonstrated that the centric fusion took place between chromosomes 6 and 15 of the RBA-banded karyotype recently proposed as « standard » for the species Capra hircus L. The C-banding pattern showed the presence of 2 blocks of constitutive heterochromatin, corresponding to the centromeres of the 2 chromosomes involved in the fusion. Silver staining revealed telomeric nucleolus organizer regions on the long arm of the two-armed chromosome.

R-banding pattern of the prometaphase chromosomes of the domestic sheep Ovis aries L.

The discovery of the RBA-banding procedure by Dutrillaux et aL (1973) has provided a remarkable improvement in the identification and description of individual chromosomes of mammals, including man. The benefits of this technique are quite evident in the family Bovidae, whose chromosomes, especially the smallest elements of the karyotype, are not easily distinguishable when G-banded; the difficulty lies in the fact that in Bovidae chromosomes, both centromeres and telomeres are mostly G-negative and, therefore, the smallest autosomes have to be identified by relying upon very few and often undefined bands.

Measurement of micronuclei by cytokinesis-block method in bovine lymphocytes

The present study was carried out in order to set up a standardized quantitative assay for spontaneous micronuclei in bovine lymphocytes. For this purpose the cytokinesis-block micronucleus (MN) method, originally proposed by Fenech and Morley (1985) for human lymphocytes, was applied to peripheral blood lymphocytes of 20 healthy cows of Italian Friesian breed. The results demonstrate that the optimal concentration of cytochalasin B to obtain the highest frequency of binucleated cells (mean = 400.26 +/- 23.76/1000 cells scored) was 6 micrograms/ml. The baseline frequency of spontaneous MN formation in 500 binucleated cells was 12.3 +/- 4.1, i.e., 3 times higher than that reported in human lymphocytes (Fenech and Morley, 1985; Scarfi et al., 1991). The possible reason(s) for this difference (sensitivity to cytochalasin B, chromosome number, environmental genotoxic pollutants) is discussed.

A new and unusual reciprocal translocation in cattle: rcp(11;25)(q11;q14-21).

A new and unusual reciprocal translocation was detected in a heifer of the Agerolese cattle breed during a routine cytogenetic screening carried out on 13 animals (2 males and 11 females) kept at the ConSDABI Conservation Center in Benevento (Southern Italy). The 13 animals investigated had a normal karyotype except for a 1-year-old female, which carried one autosome smaller than the smallest normal bovine autosomes. This small autosome showed very little C-banding in comparison to the other autosomes, while another medium-sized autosome showed 2 distinct and prominent C-bands. RBA-banding and karyotype analysis revealed that these 2 chromosomes were the result of a reciprocal translocation between chromosomes 11 and 25. FISH analysis with BAC142G06 mapping to the proximal (subcentromeric) region of both BTA25 and der11, BAC513H08 (ELN) mapping to BTA25q22dist and der25, and BAC533C11 mapping to the proximal region of BTA11 and der11 confirmed the localization of the breakpoints on band q11 (centromere) of chromosome 11 and q14–21 of chromosome 25. Ag-NOR and sequential RBA/Ag-NOR techniques detected the presence of NORs on both BTA11 and BTA25 and both der11 and der25. To our knowledge, this is the first report of a reciprocal translocation event in cattle with the breakpoint located in the centromeric region.

Sequential GTG-RBA banding pattern in prometaphase chromosomes of cattle ( Bos taurus L)

the same prometaphase chromosomes of cattle, is presented with the aim of establishing correlations between G and R bands. The results of the present investigation contributed to the establishment of new standard GTG and RBA-banded karyotypes at prometaphase level, useful for the precise identification of chromosomal abnormalities, comparative cytogenetics and gene mapping in the species Bos taurus L.