Genetics of Zoarces populations I. Three loci determining the phosphoglucomutase isoenzymes in brain tissue

Horizontal starch-gel electrophoresis has revealed three autosomal loci for phosphoglucomutase in the teleostean marine fish Z. viviparus L. In two natural populations, two of the loci are polymorphic for two common codominant alleles but a rare allele was also found in both. The third locus is dominated by a single very common allele but at least one rare allele occurs also. The genotypes of the three loci were found to be randomly combined in the populations and a segregation analysis of litters from double-heterozygous females shows that the two polymorphic loci recombine freely. Three different paternal alleles are required to account for the segregation found in a single litter; thus the mother must have mated with at least two different males. Segregations not complying with Mendelian expectations in litters from homozygous females indicate that an appreciable fraction of the females have mated with at least two males per brood.