Abstract The primary amino acid sequence of the prion protein (PrP) has previously been correlated with changes in the incubation period of subacute spongiform encephalopathies. We have analyzed the PrP gene from 65 different cattle representing 14 breeds by polymerase chain reaction and restriction enzyme analysis. Two distinct PrP alleles differing in the number of octapeptide repeats are present. The predominant genotype is homozygous for 6 octapeptide repeats. Few individuals (8) were found to be heterozygous for these repeats and only 1 animal was homozygous for the 5 octapeptide repeat allele.
Summary Tyrosinase related protein 1 ( TYRP1 ), which is involved in the coat colour pathway, was mapped to BTA8 between microsatellites BL1080 and BM4006 , using a microsatellite in intron 5 of TYRP1 . The complete coding sequence of bovine TYRP1 was determined from cDNA derived from skin biopsies of cattle with various colours. Sequence data from exons 2–8 from cattle with diluted phenotypes was compared with that from non‐diluted phenotypes. In addition, full‐sib families of beef cattle generated by embryo transfer and half‐sib families from traditional matings in which coat colour was segregating were used to correlate TYRP1 sequence variants with dilute coat colours. Two non‐conservative amino acid changes were detected in Simmental, Charolais and Galloway cattle but these polymorphisms were not associated with diluted shades of black or red, nor with the dun coat colour of Galloway cattle or the taupe brown colour of Braunvieh and Brown Swiss cattle. However, in Dexter cattle all 25 cattle with a dun brown coat colour were homozygous for a H424Y change. One Dexter that was also homozygous Y434 was red because of an ‘E+/E+’ genotype at MC1R which lead to the production of only phaeomelanin. None of the 70 remaining black or red Dexter cattle were homozygous for Y434. This tyrosine mutation was not found in any of the 121 cattle of other breeds that were examined.
Abstract Growth hormone genotype was determined using polymerase chain reaction (PCR) amplification of the growth hormone gene. Amplified DNA was digested with MspI, the resulting fragments separated by agarose gel electrophoresis and visualized with UV light following ethidium bromide staining. Undesired preferential amplification of alleles initially led to genotype misclassification. Two of 32 animals were misclassified when PCR products were compared to genomic digests probed with radiolabeled, full‐length cDNA of the bovine growth hormone gene. Intensity of allelic bands was quantified by densitometry. One allelic form (A1) consistently exhibited greater band intensity. Relative intensity of the A1 allele to the A2 allele varied from 1.5:1 to 18:1, depending on size of PCR amplified DNA and length of the 72°C phase of PCR. Differential intensity increased with increasing size of PCR amplified DNA and length of the 72°C phase of PCR. Subsequent analyses indicated that the apparent differential amplification was not primer dependent. Optimization of PCR conditions for a specific gene may result in optimization for a specific allele. This phenomenon is undesirable in genotypic analyses.
Summary. Sperm DNA isolated from sons of three extensively used US Holstein bulls was screened for differences associated with the primary gene structure of the bovine growth hormone (bGH) and prolactin (bPrl) genes. Southern blot analysis of DNA digested with 10 restriction enzymes revealed that offspring from two of the three bull families exhibited polymorphisms around the bGH and bPrl genes. Restriction fragment length polymorphisms (RFLPs) around the bGH gene were detected with five enzymes, whereas three enzymes revealed RFLPs around the bPrl gene. At least three structural differences were predicted around the bGH gene. The most common variant hybridization pattern appeared to involve an insertion/deletion located downstream of the conserved 3′ Eco RI site. The presence of RFLPs in the genes coding for these pituitary hormones within a familial line may provide the basis for genetic markers associated with lactation and mammary development.
