continually improved cytogenetic techniques (differential staining and high resolution banding techniques), complemented with the molecular genetics methods (fish and prins), enable chromosomal mutations to be accurately identified in the karyotype of the pig (Sus scrofa). the major breeding problem are balanced mutations because of their hidden nature, as they affect the animals with normal body conformation (and normal semen parameters in boars), which transfer these aberrations to the next generations and disseminate in the population. this refers to the structural rearrangements (translocations and inversions), causing developmental abnormalities and considerably reducing fertility and productivity parameters in breeding herds, which results in substantial financial losses. Routine karyotype screening using modern cytomolecular diagnostic methods is necessary due to the potential emergence of new mutations and the rapid spread of these genetic defects in the population, especially under artificial insemination conditions.
animal cell chimerism denotes the presence of two or more cell lines of different genetic origin. the most common form of chimerism, which occurs spontaneously in mammals, is the presence of two or more cell populations in animals derived from dizygotic twin or multiple pregnancies. the aim of this review is to present extensive information on XX/Xy chimerism in cattle, sheep and goats from the Bovidae family. additionally, it will discuss a methodology for a quick and accurate diagnosis of cell chimerism and make an analysis of cells obtained from gonads of animals derived from twin pregnancies which underwent an exchange of hematopoietic tissue as a result of anastomoses. the studies reviewed here led the authors to conclude that XX/Xy chimerism is generally undesirable in livestock breeding. females (freemartins) are infertile, whereas in male carriers of chimerism, the impact of this abnormality on sperm parameters is still under discussion, therefore every case of different-sex twin or multiple births should be analyzed individually.
The frequencies of spontaneous and in vitro mutagen-induced unstable chromosomal lesions were compared in the groups of subfertile cows, ewes and sows (test groups) as well as the animals without any reproductive disturbances (control groups). The mean percentage of 5-azacytidineand bromodeoxyuridine-induced defects differed statistically between the test and control groups (P≤0.01 in cattle, P≤0.05 in sheep and pigs). In the groups of animals with reproductive problems the number of defects observed in some chromosomes exceeded the expected values (calculated according to the relative chromosome length), but only in the case of X chromosome differed at the level of statistical significance. Moreover, the groups of cows analysed differed significantly as regards the number of chromatid breaks/gaps at the Xq2.4 and Xq3.1 fragile sites. The excessive chromosome instability in subfertile farm animals, particularly the X-specific loci, may result in inappropriate expression of genes determining reproductive traits as well as in the increased rate of aneuploid germ cells related to prenatal and perinatal mortality.
Two different reciprocal translocations, rcp (8;14) (p21;q25) and rcp (7;13) (q13;q46), were described for the first time in Poland in the Polish Landrace and Duroc pigs. Observation of synaptonemal complexes showed the presence of a quadrivalent composed of translocational chromosomes and their homologues. Individuals carrying translocations were characterized by normal external appearance and correct semen parameters. Analysis of fertility made on the basis of litter size demonstrated that fertility decreased by 25% in the carrier of translocation rcp (8;14) and by 52% in the carrier of translocation rcp (7;13). ZUSAMMENFASSUNG: Zum erste mal festgestelte gegenseitige Translokationen bei Schweine in Polen Bein Polnischen Landras und Duroc Schweinen wurden zum erstenmal in Polen, zwei verschiedene reciproke Translokationen-rcp (8;14) (p21;q25) und rcp (7;13) (q13;q46)-festgestellt. Anhand der Beobachtungen des Synaptonemal Complex wurde die Anwesenheit eines Tetravalent nachgewiesen, welches aus Translokationschromosomen und seinen Homologen zusammengesetzt ist. Die Translokationstiere hatten normale Exterieur und Spermaparameter. Aufgrund der Fortpflanzungsergebmissen wurden verminderte Fruchtbarkeit bei Translokationstieren rcp (8;14)-um 25% und bei Translokationstieren rcp (7;13)-um 52% festgestellt. RÉSUMÉ: Les translocations réciproques identifiées pour la prèmière fois chez les porcs levés en Pologne Chez les porcs des races Landrace et Duroc on a constaté, pour la première fois en Pologne deux translocations réciproques différentes-rcp (8;14) (p21;q25) ainsi que rcp (7;13) (q13;q46). L'observation des complexes synaptonémals a manifesté la présence du quadrivalent composé de chromosomes de translocation et de leurs homologes. Les animaux-les porteurs de la translocation ont se caractérisé par l'extérieur normal et par les paramètres réguliers du sperme. L'analyse de la fertilité expérimenté selon de la taille des portées a démontré la réduction de la fertilité pour le porteur de la translocation rcp (8;14) à 25% cependant pour les porteurs de la translocation rcp (7;13) à 52%.
The cytogenetic control system of bulls sent to AI stations has been in use in Poland since 1989 and it is aimed to eliminate from breeding the bulls and semen of sires affected by chromosome abnormalities, with provision for extension of the studies with family material. In the years 1989-2002 451 animals of Polish Red cattle were cytogenetically investigated and in this population four cases of 60,XX/60,XY leucocyte chimerism and three cases of 1;29 Robertsonian translocation had been found. The aberration carriers were not related. The next four cases of 1;29 Robertsonian translocation, recently diagnosed (2003) in a herd of Polish Red cattle, suggest the need for cytogenetic monitoring of genetic reserve breeds of cattle that would also account for females.
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