Electropherogram analysis: allelic peak height imbalances and allele drop-out

DNA evidence is often touted as irrefutable, but problems do exist. It is important to get objective analysis of DNA evidence in order to ensure that no potential issues slip through the cracks. Here are a few examples of problems that may occur. DNA samples degrade when a sample is aged or exposed to harsh conditions — often useful information for defendants. Degradation is marked by progressively falling peak heights as the amplicon size increases. Degraded samples are sometimes difficult to interpret because of the loss of peak height information (for determining issues like peak height imbalances). Degraded samples are also subject to allelic dropout. Peak height imbalances are calculated in heterozygous loci (containing two alleles). A peak height imbalance is generally considered to occur when there is greater than a 30% difference in the heights of the two peaks. A sample from a single person should contain peaks that are roughly equivalent in height, so an imbalance is indicative of a mixture. #DNA #Genetics #Electropherogram #alleles