Disturbed segregation at the transferrin locus of the deer mouse

SUMMARY Anomalous frequencies of transferrin phenotypes were found among the offspring of matings between deer mice heterozygous for the two forms of transferrin most common in natural populations. Matings involving other phenotypes produced offspring in the expected phenotypic frequencies. Selective penetration by facility, occurring only in the reproductive tract of the heterozygous females, appears to provide the most satisfactory explanation for the observations.