Characterization of the CSNIAG allele of the bovine αs1-casein locus by the insertion of a relict of a long interspersed element

The bovine CSN1AG allele is associated with alower proportion of as1-casein in milk and is characterizedby an insertion in the last noncoding exon(19th). According to DNA sequence analysis, the location,length, and origin of the insertion characterizingthe bovine CSN1AG allele have been identified.This insertion interrupts the 19th exon betweennucleotides 58 and 59, is 371 bp long, and has a highlevel of homology with relicts of long interspersedelements of retropositional origin. Northern blotanalysis shows that the inserted element is transcribedand that the number of transcripts of theCSN1AG allele is less than one-half of the number oftranscripts of the CSN1AB allele. The lower amountof as1-casein in milk obtained from cows carrying theCSN1AG allele can be explained by a reduced mRNAstability. Furthermore, a method has been developedusing polymerase chain reaction for identification ofthe carriers of the CSN1AG allele.