Frequency and distribution of rob(1;29) in eight Portuguese cattle breeds.

Cytogenetic investigations performed in eight Portuguese cattle breeds revealed the presence of rob(1;29) in both heterozygous and homozygous conditions in all, and five breeds, respectively, with variable percentages of carriers as follows: 41.0% in Arouquesa, 69.9% in Barrosa, 39.4% in Maronesa, 2.8% in Mirandesa, 8.5% in Marinhoa, 1.8% in Mertolenga, 21.3% in Raca Brava and 21.5% in Alentejana. CBA- and RBA-banding were performed to ascertain the chromosomes involved in the chromosome abnormality. A total of 1,626 animals were investigated. Reproductive parameters (number of calves per 100 cows) were higher in Mirandesa (80%) when compared with both Maronesa (75%) and Barrosa (70%) breeds, underlining that rob(1;29) reduces fertility in the carriers.

Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites.

Genotype data from 30 microsatellites were used to assess genetic diversity and relationships among 10 native Portuguese cattle breeds, American Charolais and the Brazilian Caracú. Hardy-Weinberg equilibrium was observed for all loci/population combinations except for five loci in Brava de Lide and one locus in Alentejana that exhibited heterozygote deficiency. Estimates of average observed and expected heterozygosities, total number of alleles (TNA) per breed and mean number of alleles (MNA) per locus/population were obtained. A total of 390 alleles were detected. TNA among Iberian cattle ranged from 170 to 237 and MNA ranged from 5.67 to 8.07. The highest observed heterozygosities were found in the Caracú, Maronesa, Garvonesa and Arouquesa and the lowest in Brava de Lide and Mirandesa. Estimation of population subdivision using Wright's FST index showed that the average proportion of genetic variation explained by breed differences was 9%. Neighbour-joining phylogenetic trees based on DA distances showed that the genetic relationships of present-day Portuguese native breeds are consistent with historical origins in the Brown Concave (Arouquesa, Mirandesa, Marinhoa) and Red Convex (Mertolenga, Alentejana, Garvonesa, Minhota) evolutionary groups. The Iberian Black Orthoide group, represented by Brava de Lide and Maronesa, and the Barrosã breed appeared to be more closely related to the Brown Concave group but may represent a separate lineage. The Caracú breed was not found to be closely associated with any of the native Portuguese breeds.

Frequency and distribution of rob (1;29) in three Portuguese cattle breeds.

Representative samples of Portuguese cattle from Barrosã, Maronesa, and Mirandesa breeds underwent cytogenetic investigation. Banding showed that 134 (65.0%) Barrosas, 74 (40.2%) Maronesas and 4 (1.6%) Mirandesas carried rob (1;29). The frequency of this translocation in the three breeds (39% in Barrosas, 23% in Maronesas, and 1% in Mirandesas) was in a genetic Hardy-Weinberg equilibrium for the three karyological forms (2n = 60, 2n = 59 and 2n = 58), strongly supporting the hypothesis for an ancient origin of this translocation and the hypothesis of the origin of Maronesas from Barrosã and Mirandesa cross-breeding.

A new centric fusion translocation in cattle, rob(16;18).

A Barrosã bull (Portugal) has been found to carry a new Robertsonian translocation involving chromosomes 16 and 18 of standard cattle karyotype, as demonstrated by GBG- and RBG-banding techniques. C-banding patterns revealed the dicentric nature of this translocation. A comparison between normal cattle chromosome 16 and the q-arms of translocation chromosome and river buffalo chromosome 5 revealed the same G- and R-banding patterns, with only exception of a pericentromeric G-positive band which has been lost in river buffalo 5q and conserved in normal cattle chromosome 16 and rob(16;18) q-arms.

A new Robertsonian translocation in cattle, rob(15;25).

A new Robertsonian translocation, rob(15;25), was discovered in a Portuguese Barrosa cow. The animal (2n = 59,XX) was found by G- and R-banding to be a heterozygous carrier of a centric fusion translocation involving chromosomes 15 and 25. C-banding revealed the dicentric nature of this new centric fusion. Comparison of this new translocation with the well-known Robertsonian translocation rob(1;29), which is often found in the same breed, confirmed that two different chromosomes (25 and 29) were involved in the short arms of these two Robertsonian translocations.

A cattle breed close to 58 diploid number due to high frequency of rob(1;29).

Barrosa cattle, reared in the north of Portugal primarily for meat production, number about 40,000 (about 6% of all cattle in Portugal). Their fertility (number of calves per 100 cows) varies from 60% to 80% and is lower than that of other Portuguese cattle breeds. 195 animals (28 males and 167 females), randomly selected from a large area, were sampled for cytogenetical investigation. The results were the following: (a) 68 (34.9%) animals (7 males and 61 females) had normal karyotypes; (b) 127 (65.1%) were found to be carriers of rob(1; 29), as shown by G- and R-banding; (c) 102 (52.3%) animals (17 (8.7%) males and 85 (43.6%) females) were heterozygous carriers; (d) 25 (12.8%) animals (4 (2%) males and 21 (10.8%) females) were homozygous carriers. C-banding patterns revealed one block of constitutive heterochromatin (HC) in the proximal q-arm region of the translocated chromosome.