Biology of Disease

characterized by alterations in the permeability of epithelial cell membranes

to CL–, is a very common inherited disorder, with a prevalence of one in 2000

in the UK. Mitochondrial diseases are associated largely with defects in the

oxidative phosphorylation system, leading to a variety of neurological and

neuromuscular disorders. Disorders of peroxisomes result in number of

fatal diseases that are characterized by the accumulation of very long chain

fatty acids in tissues. Lysosomal storage disorders, of which more than 40 are

known, are rare and often fatal, though the adult form of Gaucher’s disease

is usually associated with a longer life span. Diseases associated with defects

of the cytoskeleton of muscle fibers are Duchenne and Becker’s muscular

dystrophies. Mutation in genes for proteins of the cytoskeleton of erythrocytes

can lead to them being deformed and to their premature removal by the

spleen, with accompanying anemia.

QUESTIONS

1. Which of the following modes of inheritance is shown by cystic
   fibrosis?

(a) autosomal dominant;

(b) autosomal recessive;

(c) sex-linked;

(d) spontaneous mutation;

(e) none of the above.

2. Which of the following genes is associated with cystic fibrosis?

(a) EPB41;

(b) ANK1;

(c) CFTR;

(d) SPTB;

(e) Mitochondrial genome.

3. Arrange the two following lists to show the most appropriate pairings:

A-spectrin LGMD

EPB41 hereditary elliptocytosis

Hexoseaminidase A sphingomyelin

Sarcoglycans chloride channel

Niemann-Pick disease MELAS

Refsum’s disease BMD, DMD

Adrenoleukodystrophy Tay-Sachs disease

CFTR hereditary spherocytosis

Dystrophin VLCFAs

Mitochondrial gene for tRNALeu phytanic acid

4. Suggest why some mitochondrial diseases lead to myoglobinuria
   (myoglobin in the urine).


5. The accompanying graph shows the extent of hemolysis of two blood
   specimens, A and B, in response to decreasing concentrations of NaCl.
   One specimen was from a patient with hereditary spherocytosis and
   the other was a control.

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