The following three recessive genes are found in corn.  Brittle endosperm (bt1), glossy leaf (gl17), and ragged seedling (rgd1). A tri-hybrid is test-crossed producing the following offspring.

            brittle, glossy, ragged              258

            brittle, glossy                           121

            ragged                                     119

            glossy, ragged                           26

            wild-type                                 242

            brittle, ragged                              7

            glossy                                          5

            brittle                                         22

                                                            800

            a–if the genes are linked, determine the relative order and map distances (both      measured and actual).

            b–what is the coefficient of coincidence for double crossovers.

            c–Is there any crossover interference?  If so, how much?