LINKAGE ANALYSIS BY 2-DIMENSIONAL DNA TYPING

In two-dimensional (2-D) DNA typing, genomic DNA fragments are separat ed, first according to size by electrophoresis in a neutral polyacryla mide gel and second according to sequence by denaturing gradient gel e lectrophoresis, followed by hybridization analysis using micro- and mi nisatellite core probes. The 2-D DNA typing method generates a large a mount of information on polymorphic loci per gel. Here we demonstrate the potential usefulness of 2-D DNA typing in an empirical linkage stu dy on the red factor in cattle, and we show an example of the 2-D DNA typing analysis of a human pedigree. The power efficiency of 2-D DNA t yping in general is compared with that of single-locus typing by simul ation. The results indicate that, although 2-D DNA typing is very effi cient in generating data on polymorphic loci, its power to detect link age is lower than single-locus typing, because it is not obvious wheth er a spot represents the presence of one or two alleles. It is possibl e to compensate for this lower informativeness by increasing the sampl e size. Genome scanning by 2-D DNA typing has the potential to be more efficient than current genotyping methods in scoring polymorphic loci . Hence, it could become a method of choice in mapping genetic traits in humans and animals.