Comparative studies provide insight into the possible common ancestor of a gene, trace the accumulation of mutations over time and suggest selective pressures that influence the expression and functions of genes (Pennacchio and Rubin 2003) . Comparisons have provided useful predictions about which sequences are minimally essential for function as well as those that may be important on a species-specific level (Aparicio et al. 1995) . Comparative genomic computational approaches continue to identify conserved regions in non-coding sequences. The challenges will be to determine which sequences are functionally significant and to identify coordinately regulated genes and common regulatory pathways. Understanding such networks, the transcription factor binding sites and genes involved in disease states may reveal alternative points of intervention and contribute to a more predictive approach to molecular medicine.