1. (10 marks) In an E. coli
mapping experiment a cross is made between an Hfr strain that is
a⁺ b⁺ d⁺ in genotype and an F-
strain that is a^– b^– d^– in
genotype. Interrupted-mating studies show that b⁺ enters
the recipient strain last. You select for b⁺
recombinants and obtain 400 that are then tested for the presence
of the a⁺ and d⁺ alleles. The following data
were obtained:

                    
a⁺ b⁺ d⁺    
326

                    
a^–   b⁺
d⁺        2

                    
a⁺ b⁺
d^–       14

                    
a^–   b⁺ d^–
      58

                                       
400

A. (2 points) why select for
the late entering gene in this experiment?

B. (2 points) What is the gene
order (show your reasoning)?

C. (4 points) What are the
frequencies of recombination between each pair of genes? Show
calculations.

D. (2 points) Draw a map, showing map distances
(in map units) between genes.