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Milk yield and composition in cattle are typical quantitative traitswhich are influenced by environmental factors and allelic variations. K-casein is a protein expressed in milk and, due to is polymorphism, may serve as a molecular marker for yield, composition and technological properties of milk. The objective of this study was to compare the relation between the genetic marker CSN3 (k-casein) and the observed milk traits in selected cattle groups. In our study we analyzed the milk traits of 32 Romanian Brown dairy cows and 54 Romanian Simmental dairy cows. The experiments described in this paper show clear evidence that -CSN3 genotype is involved in milk protein enrichment. The CSN3 gene of BB genotype showed a grate influence on protein yield. The relation between CSN3 genotype and milk protein was found to be significant in both cattle breed.

The objective of the present study was focused on possibilities to estimate the allele and genotype frequencies of β-lactoglobulin (BLG) gene polymorphisms in dairy cattle belonging to two different genetic groups from the Research and Development Station for Bovine Raising Arad in order to have breeding programs that target an increase in the frequency of the B allele in the dairy cattle population. Genotyping was performed on 20 Romanian Spotted and 18 Brown of Maramures cattle.In order to differentiate the favorable genotype for superior composition and higher cheese yield, we used simple DNA extraction method from fresh blood and techniques based on DNA analysis, which include polymerase chain reaction and restriction fragment length polymorphisms (PCR-RFLP) methods. Employing these techniques we were able to determine the (BLG) genotype of all individuals in a given population under selection, regardless of sex, age or physiological stage. As a result, it is now possible to include information on milk protein genotypes into marker assisted selection programs and consequently improve response to selection.

Caseins are a family of milk proteins that exist in several molecular forms and arethe main proteins present in the bovine milk. Genetic variation of these proteins hasbeen associated with the quality and quantity of cheese derived from milk.This study was focused on possibilities to evaluate the frequency of the K-casein Ballele in dairy herds from the Research and Development Station for Bovine RaisingArad in order to have breeding programs that target an increase in the frequency ofthe B allele in the dairy cattle population.In order to differentiate the favorable genotype for superior composition and highercheese yield, we used simple DNA extraction method from fresh blood andtechniques based on DNA analysis, which include polymerase chain reaction andrestriction fragment length polymorphisms (PCR-RFLP) methods. Employing thesetechniques we were able to determine the k-casein genotype of all individuals in agiven population under selection, regardless of sex, age or physiological stage.As a result, it is now possible to include information on milk protein genotypes intomarker assisted selection programs and consequently improve response to selection.

The effect of simple and sequential embryo culture media on the preimplantationdevelopment of mouse nuclear transfer (NT) embryos reconstructed with cumuluscell nuclei using a mechanical NT technique was studied. Blastocyst formation ratewas evaluated using CZB medium. Nonmanipulated and sham-manipulatedparthenogenetic embryos served as controls for, respectively, the medium and thehandling technique. Rates of blastocyst formation for medium and handling controlembryos were similar in CZB (50% and 53%). Development of NT embryos wassignificantly impaired from the two-cell stage onwards, reaching the blastocyst stage ata rate of 4% in CZB. These data demonstrate not only that NT embryos are moresensitive to in vitro culture conditions than parthenogenetic control embryos but alsothat selection of culture media can influence the preimplantation development of NTembryos.

In a mutant ES cells↔ wild-type embryo chimera, ES cells behave more like epiblastcells. They can contribute to the primitive ectoderm layers, which give rise to all theembryonic tissues and some extraembryonic tissues (Beddington and Robertson,1989), but not to trophectoderm or primitive endoderm. Using transgenic ES celllines, aggregated with cleavage stage host embryo, ES cells can integrate randomlyin the embryo proper. If they will be take part in the formation of ICM (inner cellmass), it will be possible to obtain germline chimera animals. To generate ES cells↔ cleavage stage host embryo chimeras, we used (CD-1) mice as donors of hostembryos as well as recipients of manipulated embryos. For chimera production, weused fluorescent-labeled ES cell line (CD1/EGFP), because in this case we canfollow the fate of ES cells during the embryonic development. We produced thechimers using “aggregation chimera technique”. 8 cells stage zona pellucida free,mouse embryos were aggregated in an aggregation plates, with a clump of ES cells(10 – 15 cells. The chimera embryos were cultivated for 24 hours in the incubator(at 37 °C, 5% CO2 in air). The chimera blastocysts resulted after cultivation, weretransferred to the uterus of the 2.5-dpc pseudo pregnant females.

During the experiments we have carried out with imature oocyte collected from the ovarian follicles, we found a variety of oocyte-cumulus complexes. We got the following experiment in order to understand the role of cumular cells on the achievement of the cytoplasma and oocyte nucleus maturation. We select the oocytecumulus complexes collected both from cows and sows according to the number of cumular cell layers and we watched their development to the blastocyst stade. Thus, we achieved three groups of COC (oocyte-cumulus complexes). One group was made of oocyte without cumular cells, the second group had a layer of cumular cells and the third group had many layers of cumular cells. we performed an incubation of all these types of COC in TCM-199 enriched with 20% of bovine fetal serum. Because only 1,2 oocyte of the ones who lack the cumular cells layer had maturation signs during cultivation in the thermostat versus 55 and 115, respectively, of the ones that had many cellular layers, presents a solid evidence that cumular cells are indispensable for the maturation and even to the fecundation process. The cumular cells perform a decisive role on the cytoplasma and oocyte nucleus maturation process.