Analysis of mouse embryonic gene library for the frequency of single and multiple copy genes.

A gene library was constructed from embryonic mouse DNA by ligating DNA fragments generated by partial Eco RI digestion with Charon 4A vector and in vitro packaging. A special consideration was given to randomization of target DNA. The general applicability of a gene library prepared in this manner was assessed through cloning a variety of genes of known reiteration frequency in the mouse genome. The survey included a single copy gene--C region of the immunoglobulin heavy chain, and genes that appear in more than one copy--V region of the immunoglobulin light chain genes and the endogenous retrovirus related genes. In all cases tested the frequency of clone isolation was in good agreement with the expected incidence based on the number of genome equivalents screened and the reiteration frequency of that particular gene. Moreover, we found no preference with regard to the clonability of genes contained in fragments of a wide-size range.