Forensic DNA Typing Protocols: A Review of Methods and Applications
Forensic DNA typing is the process of identifying individuals based on their DNA profiles, which are derived from specific regions of the genome that vary among individuals. Forensic DNA typing can be used for various purposes, such as criminal investigations, paternity testing, identification of missing persons, mass disasters, and ancestry inference.
Forensic DNA typing protocols are the methods and procedures that are used to collect, preserve, extract, amplify, analyze, and interpret DNA samples for forensic purposes. Forensic DNA typing protocols can vary depending on the type and quality of the biological material, the type and number of genetic markers, the type and sensitivity of the analytical instruments, and the type and complexity of the statistical analysis.
In this article, we will review some of the forensic DNA typing protocols that are available in the literature, and highlight their advantages and limitations. We will also discuss some of the applications and challenges of forensic DNA typing in different scenarios.
Collection and Preservation of Biological Samples
The first step in forensic DNA typing is to collect and preserve biological samples that contain DNA from the individuals of interest. Biological samples can include blood, saliva, semen, hair, skin cells, bones, teeth, nails, etc. The collection and preservation of biological samples should be done carefully to avoid contamination, degradation, or loss of DNA.
Some of the protocols for collection and preservation of biological samples are:
Collection of Samples for DNA Analysis: This protocol describes how to collect different types of biological samples using swabs, filters, or other devices, and how to store them in appropriate containers and conditions[^1^].
Preservation of and DNA Extraction from Muscle Tissue: This protocol describes how to preserve muscle tissue samples using ethanol or silica gel packets, and how to extract DNA from them using a modified phenol-chloroform method[^4^].
Extraction of DNA from Skeletal Remains: This protocol describes how to extract DNA from skeletal remains using a silica-based method or a ChelexÂ-based method.
Extraction of DNA from Human Skeletal Material: This protocol describes how to extract DNA from human skeletal material using a modified organic method or a QIAampÂ DNA Investigator Kit.
Extraction and Purification of DNA
The next step in forensic DNA typing is to extract and purify DNA from the biological samples. Extraction and purification of DNA involve breaking down the cellular structures that contain DNA, removing proteins and other impurities that interfere with DNA analysis, and concentrating and stabilizing the DNA molecules.
Some of the protocols for extraction and purification of DNA are:
DNA Extraction: Organic and Solid-Phase: This protocol describes how to extract DNA from biological samples using an organic method (phenol-chloroform) or a solid-phase method (silica columns).
The Development and Use of Internal Amplification Controls (IACs) with DNA Profiling Kits for Forensic DNA Analysis: This protocol describes how to use IACs to monitor the efficiency and quality of DNA extraction and amplification.
NucleoSpinÂ XS Columns for DNA Concentration and Clean-Up: This protocol describes how to use NucleoSpinÂ XS columns to concentrate and clean up DNA samples after extraction or amplification.
Purification of PCR Products to Improve STR Profiles: This protocol describes how to purify PCR products using ExoSAP-ITÂ reagent to remove excess primers and dNTPs that can affect STR analysis.
Amplification and Analysis of Genetic Markers
The final step in forensic DNA typing is to amplify and analyze genetic markers that are informative for individual identification. Genetic markers are regions of the genome that have variations among individuals. The most commonly used genetic markers for forensic DNA typing are short tandem repeats (STRs), which are sequences of 2-6 nucleotides that are repeated consecutively. Other types of genetic markers include single nucleotide polymorphisms (SNPs), insertion-deletion polymorphisms (INDEL aa16f39245