C

Cell lines

Different human chromosomes are lost in different cell lines.

Different human chromosomes are lost in different cell lines.

7.18 Somatic-cell hybridization can be used to determine which chromosome contains a gene of interest.

bridization procedure are deficient in TK, but can produce HPRT (the cells are tk~ hprt+); the human cells can produce TK but are deficient for HPRT (they are tk+ hprt~). On HAT medium, the mouse cells do not survive, because they are tk~; the human cells do not survive, because they are hprt~. Hybrid cells, on the other hand, inherit the ability to make HPRT from the mouse cell and the ability to make TK from the human cell; thus, they produce both enzymes (the cells are tk+ hprt+) and will grow on HAT medium.

human fibroblast hprt +/tk -

mouse tumor cell hprt- /tk+

human fibroblast hprt +/tk -

mouse tumor cell

hprt cells die

tk -cells die tk -cells die

Hybrid cells survive

7.19 HAT medium can be used to separate human-mouse hybrid cells from the original hybridized cells.

To map genes using somatic-cell hybridization requires the use of a panel of different hybrid cell lines. The cell lines of the panel differ in the human chromosomes that they have retained. For example, one cell line might possess human chromosomes 2, 4, 7, and 8, whereas another might possess chromosomes 4, 19, and 20. Each cell line in the panel is examined for evidence of a particular human gene. The human gene can be detected either by looking for the protein that it produces or by looking for the gene itself with the use of molecular probes (discussed in Chapter 18). Correlation of the presence of the gene with the presence of specific human chromosomes often allows the gene to be assigned to the correct chromosome. For example, if a gene was detected in both of the aforementioned cell lines, the gene must be on chromosome 4, because it is the only human chromosome common to both cell lines ( FIGURE 7.20).

Human chromosomes present

Cell line

Gene product present

0 0

Post a comment