Knobbly, a new dominant mutation in the mouse that affects embryonic ectoderm organization.

Knobbly, Fu Kb , a dominant mutation on chromosome 17 of the mouse, causes a kinked tail in heterozygotes and embryonic lethality at about nine days in homozygotes. Abnormal organization of the embryonic ectoderm is first apparent at about embryonic day 7, and the retarded and malformed embryos die by mid 9 days. Kink, Fu Ki , a dominant gene that maps in the same region, is also an embryonic lethal in homozygotes; heterozygotes have kinked tails and often a circling gait. We have shown Fu Kb and Fu Ki are allelic; the Fu Kb /Fu Ki compound dies at the same time as Fu Kb /Fu Kb embryos with the same morphological syndrome. The Fu Kb phenotype is not seen in offspring in expected ratios. The Fu Kb males may have a low transmission ratio or penetrance may be incomplete.