suppose we have three linked genes, all of which control different aspects of the same phenotype. We perform a testcross of a triple heterozygote (a+b+c+/a b c) with a triply homozygous recessive (a b c/a b c) and then count the number of progeny in each of the phenotypic classes. There are a total of 550 progeny. Arrange the genotype in the table, define the origin(parental, single cross-over progeny and double-crossover progeny) and determine the order of the genes on the chromosome.