CASE FILES: BIOCHEMISTRY
A nsw ers
D. Because cystic fibrosis leads to pancreatic damage and diminution
of the ability to secrete HCO3- and pancreatic digestive enzymes with
the result that fat and protein are absorbed poorly. Retinol is a fat-
soluble vitamin that must be absorbed along with lipid micelles; other
fat-soluble vitamins are E, D, and K. The other vitamins listed are
water-soluble and their absorption is not significantly affected.
D. Restriction length fragment polymorphism analysis detects muta-
tions in the DNA that either introduce or eliminate a recognition site
for a restriction enzyme. This is detected by performing a Southern
blot analysis on patient DNA after incubation with a specific restric-
tion enzyme and comparing it to one performed on DNA obtained
from a normal gene.
A. If the mutation is known, radioactive or fluorescent probes can be
produced for alleles that contain the mutation and for those that have
a normal DNA sequence. The samples of DNA are spotted onto nitro-
cellulose paper in narrow bands. The paper is then incubated with the
probe either for the normal or the mutant sequence. Since it does not
involve an electrophoresis step, this type of analysis is much less
time-consuming (and less expensive).
B IO C H E M IS T R Y PE A R L S
Northern blot uses oligonucleotide probes to identify RNA,
Southern blot identifies DNA, and Western blot identifies protein
Recombinant DNA technology allows for a transfer of a DNA frag-
ment of interest into a self-replicating genetic element such as a
bacterial plasmid or virus.
Restriction length fragment polymorphism analysis detects muta-
tions in the DNA that either introduce or eliminate a recognition
site for a restriction enzyme.
Oligonucleotide probes can be directed against precise DNA
sequences and yields a quick and accurate result.
Schwiebert LM. Cystic fibrosis, gene therapy, and lung inflammation: for better or
worse? Am J Physiol Lung Cell Mol Physiol 2004;286: L715-L716.
Welsh MJ, Ramsey BW, Accurso F, et al. Cystic fibrosis. In: Scriver CR, Beaudet
AL, Sly WS, et al., eds. The Metabolic & Molecular Bases of Inherited Disease,
8th ed. New York: McGraw-Hill, 2001.