Chapter 12, Problem 9P

Suppose you performed a fluorescence in situ hybridization experiment (FISH) on chromosomes from a human cell using a probe corresponding to a gene located near (but not at) the telomere of the q arm of chromosome 4.

a.	On the following idiogram, which shows only chromosomes 1–5 contained in this diploid cell, indicate the location of all fluorescent signals.

 

b.

Compare your idiogram with the result of the FISH experiment shown in Fig. 12.9a. Why are the chromosomes scattered in Fig. 12.9a, rather than being present in neatly arranged pairs of homologous chromosomes as in the idiogram? Do you think it is likely that the gene whose DNA was used as a probe in Fig. 12.9a is found on the q arm of human chromosome 21?