A method for kappa-casein genotyping of bulls

Analysis of polymorphism in the bovine casein genes by use of the polymerase chain reaction

Methods have been devised for detecting polymorphisms in the bovine beta- and kappa-casein genes using the polymerase chain reaction (PCR) followed either by restriction enzyme digestion (to reveal a restriction fragment length polymorphism (RFLP] or by hybridization of an allele-specific oligonucleotide. These methods, as well as being faster and more sensitive than traditional RFLP methods, are of more general applicability since they can detect any change in DNA sequence. They require only a small sample of blood or semen and are applicable to animals of any age or sex. These methods make possible large-scale screening and thus selection for alleles at these loci. Typing of blood DNA can give erroneous results when the animal concerned is a twin; however, this can be overcome by retesting using milk or semen. Analysis of the kappa-casein genotype of Holstein-Friesian bulls gives frequencies for the A and B alleles of 0.80 and 0.20 respectively. Selection in favour of the B allele, which is superior for cheese production, could thus have a large effect. The A3 and B alleles at the beta-casein locus have been shown to be rare in the Holstein-Friesian population. Linkage disequilibrium exists between beta-casein B and kappa-casein B.

Kappa-casein polymorphisms in Indian dairy cattle and buffalo: a new genetic variant in buffalo

We screened 57 Sahiwal cattle (Bos indicus) and 53 Murrah, 19 Nili-Ravi and 11 Egyptian buffaloes (Bubalus bubalis) to detect the polymorphisms at kappa-casein (CSN3) gene using the polymerase chain reaction (PCR). CSN3 A and B alleles were identified by PCR-RFLP using the restriction enzymes that detect the underlying nucleotide changes at codon 136 (Taql) and at codon 148 (HindIII or HinfI) in cattle. The frequency of CSN3 B allele in the Sahiwal cattle was estimated as 0.16 with no homozygous BB animal. Using the same set of primers as used in the Sahiwal cattle, a part of exon IV of buffalo CSN3 gene was amplified, but restriction enzyme analysis using HindIII/HinfI and TaqI did not reveal any polymorphism. However, DNA sequencing of the amplified fragment (GenBank Acc. No. U96662) revealed one polymorphism at codon 135 (ThrACC -->I1eATC) in buffalo; the frequencies of 135 Thr/Ile alleles were estimated as 0.88 and 0.12, respectively.

Milk protein polymorphisms in Brazilian Zebu cattle

Five bovine milk protein polymorphisms were studied in Zebuine cattle raised in Brazil, through horizontal electrophoresis on starch gel containing urea and 2-mercaptoethanol, using basic and acidic buffer systems. Allelic frequencies for <FONT FACE="Symbol">a</FONT>-La, <FONT FACE="Symbol">b</FONT>-Lg, <FONT FACE="Symbol">a</FONT>S1-Cn, <FONT FACE="Symbol">b</FONT>-Cn and <FONT FACE="Symbol">k</FONT>-Cn loci were estimated in six Gyr herds (N = 283), six Guzerat herds (N = 205), one Nelore herd (N = 17) and one Sindi herd (N = 22), all from São Paulo or Minas Gerais State, Brazil. Genotypic frequencies observed for each locus and breed studied are in accordance with the assumption of genetic equilibrium, demonstrating absence of high inbreeding levels for the breeds tested. The FST value found indicated significant genetic differentiation among breeds; however, the Gyr and Guzerat herds showed significantly different gene frequencies. Genetic distance estimates among zebuine breeds studied and the Holstein breed, taken as a reference for a taurine breed, showed strong differences between these two racial groups

Simultaneous analysis of bovine kappa-casein and BLAD alleles by multiplex PCR followed by parallel digestion with two restriction enzymes

An improved and simplified method allowing simultaneous genetic typing of kappa-casein and CD 18 (bovine leucocyte adhesion deficiency; BLAD) loci has been developed. The method is based on the simultaneous amplification of fragments of the two groups of alleles by multiplex PCR, and on a concurrent, parallel digestion of the products by two restriction enzymes (PstI and HaeIII) in the same incubation buffer. Digestion with PstI distinguishes kappa-casein A and B alleles and does not cut within any of the BLAD alleles, while digestion with HaeIII allows the differentiation between normal and mutant allele variants of the CD18 locus. All combinations of the known mutants of the two alleles, characterized to the regions amplified and resulting in phenotypic effect, could be detected by electrophoretic separation performed on the same agarose gel owing to the vast differences in the length of the restriction fragments.

Phenotyping of bovine milk proteins by reversed-phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method for the separation of the most common and some less common genetic variants of the bovine caseins is described. When the method is used for analysing clarified skim milk, simultaneous identification of casein variants and major they protein variants can be effected in a single run. The potential of the method for quantitative application is discussed.

Genomic analysis of the major bovine milk protein genes

The genomic arrangement of the major bovine milk protein genes has been determined using a combination of physical mapping techniques. The major milk proteins consist of the four caseins, alpha s1 (CASAS1), alpha s2 (CASAS2), beta (CASB), and kappa (CASK), as well as the two major whey proteins, alpha-lactalbumin (LALBA) and beta-lactoglobulin (LGB). A panel of bovine X hamster hybrid somatic cells analyzed for the presence or absence of bovine specific restriction fragments revealed the genes coding for the major milk proteins to reside on three chromosomes. The four caseins were assigned to syntenic group U15 and localized to bovine chromosome 6 at q31-33 by in situ hybridization. LALBA segregated with syntenic group U3, while LGB segregated with U16. Pulsed-field gel electrophoresis confirmed genetic mapping results indicating tight linkage of the casein genes. The four genes reside on less than 200 kb of DNA in the order CASAS1-CASB-CASAS2-CASK. Multiple restriction fragment length polymorphisms were also found at the six loci in three breeds of cattle.