Dr Andrew Belmont's group from the University of Illinois at Urbana-Champaign, have developed a method to tag specific chromosome sites with fluorescent proteins, which is described in the latest edition of the journal Cold Spring Harbor Protocols .

Once the tagged cell lines have been established, the chromosomal regions of interest can be visualized with a fluorescently labeled Lac repressor protein, which binds to the lac operator sequence. This allows the scientists to examine the structure of the chromatin and to observe the activity of the chromosomes during replication and transcription.

As well as isolating stable cell clones with varying transgene copy numbers, the technique can also be used to visually screen large numbers of stable cell clones to isolate rare clones containing labelled chromosomal regions with desired features.

Belmont's lab and others have used this technique to investigate the structure and dynamics of chromatin in live cell cultures, yeast, and various multicellular organisms, including C. elegans, Drosophila, and Arabidopsis.

A second featured method in same journal describes how to perform immunohistochemistry in whole mouse embryos, which allows scientists to examine the three-dimensional distribution of a protein during specific stages of development. It can be used to detect endogenous proteins as well as the products of transgenes.

The immunohistochemistry protocol was derived from methods used to examine embryonic development in other species, including Xenopus and Drosophila. It describes several tricks to chemically and physically manipulate the embryos so that the antibodies, which detect the protein of interest, can efficiently penetrate the embryonic tissue.