You Are Studying an Individual with Very Low Levels of Insulin

You are studying an individual with very low levels of insulin in her blood. Further analysis indicates that cells of her pancreas are producing normal levels of this protein, but most of it is accumulating in the cytoplasm rather than being secreted from the cells. Which hypothesis to explain this observation makes the most sense?

A) A small deletion has removed the nucleotides that code for the signal sequence at the amino terminus of the protein.
B) A missense mutation has caused premature termination during translation of this protein.
C) A chromosomal segment that includes the gene for insulin has been inverted.
D) A two-base deletion near the middle of the gene has altered the reading frame during translation of the protein.
E) A missense mutation has altered the ribosome-binding sequence at the 5' end of the mRNA.