Question

Required information Shown below are the maps of a series of rll-deletion strains (1-5). The deleted region is indicated as (...) and the intact region as 1 2 ...........) 3................. 4 5 rll-phage strains A-E have point mutations in the ill region. E.coli (A) cells are coinfected with one phage that has a deletion and one phage that has a point mutation. The presence of wild-type progeny phage is assessed by the presence (+) or absence (o) of plaques. 12345 A+ 0 +++ BO + + + + C++ + 0 + D ++0++ E + + 0 + 0 Indicate the order of the point mutations in the rllregion. Multiple Choice BADCE CEADB

Answer 1

When deletion and mutation happened at same site,it leads to absence of plaques.

Upon observing crosses of mutant strains and deleted strains,you can know the order of mution.

3rd one has deletion in the initial region of the gene.Cross between 3rd and strains D , E resulted in absence of plaques.E gave negative for plaques when crossed with 5th strain also.So,Order of mutation is DE.

Similarly,one can identify that crosses of 1,2 and 4 with strain B,Aand C gave negative for plaques.

So order is B,A,C.

So overall order of mutation is DEBAC.