Selective breeding drives ectopic bone penetrance downward and upward.Full-sibling heterozygous mef2ca pairs were intercrossed and their homozygous mutant offspring were scored for penetrance of ectopic bone near the opercle. Mutant progeny penetrance scores were assigned to each breeding pair. Parents are color coded for offspring penetrance on this pedigree. Heterozygous offspring from selected pairs were raised for the next round of selection. A single low-penetrance individual from generation four was crossed to a double-transgenic mef2ca wild-type unselected individual (black circle). Indicated individuals from recent generations in the low-penetrance line are viable as mef2ca homozygous mutants. Indicated pairs from recent generations in the high-penetrance strain produce heterozygous offspring with mef2ca-associated phenotypes. Uncolored circles represent homozygous mutant adults that were recovered but were not tested for mutant offspring ectopic bone phenotype penetrance.
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