Question

A mutant plant with white flowers exists that lacks red anthocyanin pigment, normally made by enzyme P. Indeed the petal tissue lacks all detectable activity for enzyme P. Despite the lack of enzyme activity, a study of homozygous mutant cells using antibodies against the wild-type enzyme demonstrated that the cells homozygous for the mutation still had the enzyme (i.e., the antibody showed the presence of the enzyme). Which statement below could most likely explain these results?

A )The mutant had another gene the researcher was not aware of which produced an enzyme that could function like the mutated enzyme.

B)The mutant cells likely had large scale chromosomal mutations that resulted in the expression of some gene similar to the gene for enzyme P.

C)The mutant allele must have had a nonsense mutation that resulted in complete formation of a non-functioning enzyme

D)The mutant allele must only have missense mutations that simply knocked out enzyme function yet the enzyme would still bind to the antibody

   E) None of the answers is correct

Answer 1

A missense mutation leads to change in the amino acid sequence. If the amino acid which is substituted due to a mutation is different from the original amino acid, the result shows a non-functional protein. Due to this non-functional protein in missense mutations leads to lack of red colored anthocyanin pigment and results in white flowers. The correct option is D. The mutant allele must only have missense mutations that simply knocked out enzyme function, yet the enzyme would still bind to the antibody