History Lethal allele

punnett square agouti gene in mice, demonstrating lethal recessive allele.

lethal alleles first discovered lucien cuénot in 1905 while studying inheritance of coat colour in mice. agouti gene in mice largely responsible determining coat colour. wild-type allele produces blend of yellow , black pigmentation in each hair of mouse. yellow , black blend may referred agouti in colour. 1 of mutant alleles of agouti gene results in mice lighter, yellowish colour. when these yellow mice crossed homozygous wild-type mice, 1:1 ratio of yellow , dark grey offspring obtained. indicated yellow mutation dominant, , parental yellow mice heterozygotes mutant allele.

by mating 2 yellow mice, cuénot expected observe usual 1:2:1 mendelian ratio of homozygous agouti heterozygous yellow homozygous yellow. instead, observed 1:2 ratio of agouti yellow mice. unable produce mice homozygous yellow agouti allele.

it wasn’t until 1910 w. e. castle , c. c. little confirmed cuénot’s work, further demonstrating 1 quarter of offspring dying during embryonic development. first documented example of recessive lethal allele.