Question

The table below presents the ability of five strains of Neurospora crassa that are deficient in arginine biosynthesis to grow on media supplemented with molecules that are biochemical intermediates in the arginine synthesis pathway (“+” = growth, “-“ = no growth).

a) Based on these data, diagram both the biochemical intermediates and genes in the arginine synthesis pathway.

Mutant strain               minimal media             +arginine         +citrulline            +ornithine

argA                                        -                              +                       -                          -

argB                                        -                              +                       +                        -

argC                                        -                              +                       +                        +

argD                                        -                              +                       -                          -

argE                                        -                              +                       +                        -

b) All of these mutations in the arginine biosynthesis pathway are recessive to wild-type alleles. If you cross all five strains to each other (10 crosses), which crosses will produce strains that will be able to grow on minimal media?  

Answer 1

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