Recombinant DNA Technology Problem Set

Problem 8: Huntington's disease

Tutorial to help answer the question

The data below shows the results of electrophoresis of PCR fragments amplified using probes for the site which has been shown to be altered in Huntington's disease. The male parent, as shown by the black box, got Huntington's disease when he was 40 years old. His children include 6 (3,5,7,8,10,11) with Huntington's disease, and the age at which the symptoms first began is shown by the number above the band from the PCR fragment.

In the Figure showing data on Huntington's disease, which of the following conclusions is valid:

A. No relationship between age of onset of disease and the migration rate of PCR fragments.
B. A shorter PCR fragment predicts early onset of Huntington's disease.
C. Increased length of the amplified PCR fragment predicts early onset of Huntington's disease.
D. Huntington's disease must be contagious since many of the children have the disease.
E. None of the above.


Relationship between the number of CAG repeats and the age of onset of the disease

The PCR amplified region shows a correlation between size of the fragment, a measure of the number of times CAG is repeated, and the age of onset. Larger fragment size correlates with earlier disease.

The Biology Project
University of Arizona
Updated: July 15, 1999
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