A rapid procedure for isolating genomic DNA from milk samples has
been
devised, based on the use of Chelex resin. By using this protocol, genomic
DNA was
extracted from milk samples from 15 cows and 15 goats. The suitability
of these
DNA preparations as a template for performing the polymerase chain reaction
(PCR)
was tested by amplifying three different loci of the bovine genome: exon
4 of the
κ-casein gene and the INRA5 and INRA23 microsatellites,
together with two others:
exon 19 of the αs1-casein gene and exon 2 and
part of intron 2 of the DRB gene of
the caprine genome. No amplification products could be obtained from any
samples
at 30 cycles. In contrast, at 45 cycles the number of amplified samples
ranged from
86 to 100% and at 65 cycles all the DNA targets were amplified, indicating
that the
number of cycles was a critical factor to be optimized for obtaining the
desired PCR
target. These results suggest that this method may be a useful tool for
analysing
genetic polymorphism at the DNA level by PCR and relating it to milk composition
and other traits of economic interest.