GENE EXPRESSION ANALYSIS

The invention provides a method and materials for analyzing the frequency of sequences in a population of polynucleotides, such as a cDNA library. A population of restriction fragments is formed which is inserted into vectors which allow segments to be removed from each end of the inserted fragments. The segments from each restriction fragment are ligated together to form a pair of segments which serves as a tag for the restriction fragment, and the polynucleotide from which the fragment is derived. Pairs of segments are excised from the vectors and ligated to form concatemers which are cloned and sequenced. A tabulation of the sequences of pairs provides a frequency distribution of sequences in the population.