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STR Data Analysis and Interpretation for Forensic Analysts

Dye Blobs

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Image of Dye Blob
National Institute of Justice (NIJ) (see reuse policy).

Disassociated primer dyes, more commonly referred to as dye blobs, are fairly common in STR analysis. While it isn't entirely understood why dye blobs occur, evidence suggests that the fluorescent dye tags attached to the primers begin to break down over time.01 Disassociated primer dyes can show up in the sample analysis range and can mask true data. Dye blobs are usually wider than real peaks and are typically only seen in one color. When the manufacturer's specifications for storage of amplification kits are followed, problems with disassociated primer dyes can be avoided.

If problems persist, the sample can be reamplified or a filter unit clean-up step (e.g., link to Microcon® 100) can be performed. Amplified fragments of DNA will attach to the membrane while the disassociated primer dyes pass through the membrane and are filtered out of the sample.

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