NIJ Training Course for Forensic DNA Officers of the Court: Partial Profiles in DNA Identity Testing

When a DNA sample is particularly weak or  degraded, only some of its alleles yield visible peaks after amplification, but those that  do match alleles in the sample to which it is being compared. This is known as a partial profile  notice that it is not The same as non-matching profiles, although not all of the alleles in the  complete sample can be confirmed as matching, the partial sample likewise does not  display any alleles that do not match. The reason that the shorter DNA  fragments are the ones to appear is because the longer fragments are the  less prevalent in a degraded sample.  Only small fragments have remained undamaged, like  the crumbs in the bottom of a potato chip bag.