Recessive mutant alleles of an x-linked gene in Drosophila, crossveinless (cv), prevent the development of supporting structures in the wings. Recessive mutant alleles of another x-linked gene, vermilion (v) cause a bright red eye phenotype (the wildtype eye colour is brick red). The location of an x-linked recessive lethal gene (l) was tested in relation to the cv and v loci. A female heterzygote for the lethal was mated to a male carrying cv and v. F1 heterozygous females ( l/cv v) were testcrossed to males from the cv v strain and the following percentages of phenotypes were observed in the progeny:
Phenotype: FEMALES Males
Wildtype 38.8 0.3
Crossveinless, Vermilion 38.8 77.3
Crossveinless 11.2 7.7
Vermilion 11.2 14.7
a) what is the linkage order of the three genes?
b) what is the coefficient of coincidence?