Problem:

Question 1: define the following terms as applied to light microscopy:

1) diameter of field.

2) objective lens aperture

Question 2: Analysis of the DNA of the Phenylalanine hydroxylase (PAH) gene in a patient with phenylketonuria revealed a mutation in the protein coding region whose predicted effect would be to replace the amino acid aspartic acid, with histidine. Nevertheless, no mutant protein could be found in the patient's cells. Briefly explain how this could happen.

Include source of information for best answer.