Human COT DNA decreases false positive signals in Microarrays, in situ Hybridizations, and Southern blots by acting as a blocking agent for repetitive sequences. EURx COT DNA has been optimized for a size range of 50 to 300 base pairs which represents the theoretical maximum size for repetitive sequences. 0,5 mg is sufficient for 5 to 10 Southern or 500 in situ hybridizations.