Human Genetics Problem Set
Problem 12 Tutorial: Somatic cell hybrids
By examining a number of somatic-cell hybrid lines for
enzyme activities and their human chromosome constitution, scientists
on which human chromosome the gene for a particular enzyme is
Somatic cells from two animal species may be fused to form a hybrid cell in culture. Nuclei can subsequently fuse to form a somatic-cell hybrid. Human and rodent cell fusions are important reagents for human genetics. The resulting human-rodent hybrid cells will often lose most of the chromosomes from one of the species, e.g. most of the human chromosomes, but continue to express the genes from all remaining chromosomes.
Tay-Sachs disease is a genetic disease caused by a defect in the enzyme for hexosaminidase A. Normal hexosaminidase A activity can be assayed in extracts from cultures of somatic cell hybrids.
Assume that you are studying three different somatic cell hybrid cultures.
One cell line has only human chromosomes 1, 15 and 9.
All three cell lines have human hexosaminidase A activity. You could conclude that the gene for the human enzyme was located on chromosome 15, the only human chromosome common to all three somatic cell hybrid cultures.
A second has 15, 10, and 12.
A third cell line has only human chromosomes 4, 15, and 17.
The Biology Project
University of Arizona
Revised: November 5, 1998
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