A cross in corn is carried out with three linked genes in a triply heterozygous genotype for the alleles pairs (A, a), (D, d), and (R, r). The dominant allele A results in red leaves; aa plants have green leaves. The dominant allele D results in tall plants; dd plants are dwarfed. The dominant allele R results in ragged leaf margin; rr plants have smooth leaf margins. The triply heterozygote is crossed with homozygous recessives for all three alleles, and the following phenotypes of progeny are observed. Assume that interference in each interval is complete, so that the map distance in centimorgans (cM) corresponds to the percent recombination,
Red, tall, ragged 265
Red, tall, smooth 24
Red, dwarf, ragged 120
Red, dwarf, smooth 90
Green, tall, ragged 70
Green, tall, smooth 140
Green, dwarf, ragged 16
Green, dwarf, smooth 275
Total 1000
a) What is the order of genes on the chromosome?
b) What is the shortest map distance between adjacent genes?
c) What is the longest map distance between adjacent genes?
d) What is the value of interference?