The unravelling of human genome sequence gives a new opportunity to investigate the role of repetitive sequences in gene regulation. Among the various types of repetitive sequences, the dinucleotide (TG/CA)_n repeats are one of the most abundant in human genome and exhibit polymorphism. Early on, it was observed that the (TG/CA)_n repeats could modulate gene expression and has the propensity to undergo conformational transitions in in vivo conditions. Recent reports describe the role of polymorphic (TG/CA)_n repeats in gene regulation in several genes. In this work, we have analysed the distribution of (TG/CA)_n (n ≥ 6) repeats in human ?housekeeping genes? on which recently released Gene Chip data is available. Our results indicate that (i) The number of short intragenic (TG/CA)_n repeats is significantly higher than the number of long repeats (ii) the proportion of genes with (TG/CA)_n repeats (n ≥ 12 units) had lower mean expression levels compared to those without these repeats, (iii) the genes belonging to the functional class of ?signalling and communication? had a positive association with repeats in contrast to the genes belonging to the ?information? class that were negatively associated with repeats.

Key words: TG/CA repeats, Repetitive DNA, Housekeeping genes, Expression, Polymorphic repeats, Z-DNA, Microsatellite.