COMPUTER-AIDED SEARCH FOR CODOMINANT MARKERS IN COMPLEX HAPLOID DNA BANDING-PATTERNS - A CASE-STUDY IN ABIES-ALBA MILL

A genetic trait defines a gene marker in a collection of diplophase in dividuals only if each phenotype is produced by only a single genotype . This requires codominance as the mode of gene action at each of the involved loci Ias opposed to dominance) and the absence of epistasis. Two computer programs are presented that aid in inheritance analysis o f complex DNA banding patterns of single diploid individuals by search ing the banding patterns of their haploid gametophytes for pairs of se gregating bands representing codominant alleles of a locus as well as for single hands showing dominance over a ''null allele'' defined as a bsence of the band. The program MATRIX(3)) encodes densitometrical dat a obtained from DNA banding patterns as a 1/0 matrix. The program CoDo (3)) searches this matrix for pairs of bands showing 1:1 segregation a nd for single bands showing 1:1 segregation with a null allele. This s ystem is demonstrated on both a fictitious data set and on banding pat terns obtained by PCR using a primer pair designed from an M13 bacteri ophage sequence in an individual of Abies alba (MILL.) and the haploid primary endosperm of a sample of its seeds. For the latter, no band p air showed codominance of gene action, but several bands were suggeste d for dominance. Reasons for the small number of bands showing 1:1 seg regation are discussed.