199.A 52-year-old woman patient presents with severe blistering over her
buttocks. Analysis of sera with immunofluorescence demonstrates autoanti-
bodies localized as shown in the accompanying photomicrograph. A biopsy
indicates extensive inflammatory infiltrates with numerous eosinophils present.
You are asked to look at the biopsy. The underlying cell biological mechanism
most likely involves an abnormality in which of the following structures?
306 Anatomy, Histology, and Cell Biology
a. Macula adherens
b. Hemidesmosomes
c. Gap junctions
d. Zonula occludens
e. Zonula adherens
200.A boy is born with blonde hair, blue eyes and very fair complexion,
dramatically lighter features than both of his parents. A PKU test is posi-
tive. The boy’s lighter skin and hair is most likely due to which of the
following?
a. Fewer melanocytes differentiating from the neural crest
b. Reduced proliferation of melanocytes in the basal layer of the epidermis
c. Elevated levels of tyrosinase in melanocytes
d. Deficiency in tyrosine in keratinocytes throughout the epidermis
e. Competitive inhibition of phenylalanine for tyrosinase in melanocytes
(Micrographcourtesy of Dr. Kristin M. Leiferman and the University of Utah, Department of
Dermatology site: http://uuhsc.utah.edu/derm/.))