A cross is made between 2 E. coli strains: Hfr arg+ bio+ leu+ (x) F- arg- bio- leu-. Interuppted mating studies show that arg+ enteres the recipient last, so arg+ recombinants are selected on a medium containing bio and leu only. The recombinants are tested for the presence of bio+ and leu+. The followning numbers of individuals are found for each genotype:

arg+ bio+ leu+ 320
arg+ bio+ leu- 8
arg+ bio- leu+ 0
arg+ bio- leu- 48

What is the gene order? What are the map distances in recombination units.