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Applied Biosystems and Promega manufacture most forensic STR DNA amplification kits. More recently, Qiagen has also produced a commonly used STR DNA amplification kit. Each manufacturer has modified their kits to meet the changing needs of the forensic science community.
Read more about Locus Selection in this course.
Each manufacturer has independently developed different primer sets for the Combined DNA Index System (CODIS) core loci. It is possible, albeit rare, to have one set of primers successfully amplify a locus while another fails. The failures are primarily due to primer binding site mutations and the result is a null allele.02
In general, a primer binding site mutation results in a homozygous profile for an actual heterozygote: this is called a "null allele". The manufacturers have introduced additional primer sets for their kits in an effort to minimize the occurrences of null alleles. When comparing DNA profiles developed from the different manufacturers' kits, it is important to take this into account.
For example, if a kit from manufacturer A types a locus as "12, 14" and a kit from manufacturer B types the same locus as "12" this difference may likely be due to a null allele.
Additional Online Courses
- What Every First Responding Officer Should Know About DNA Evidence
- Collecting DNA Evidence at Property Crime Scenes
- DNA – A Prosecutor’s Practice Notebook
- Crime Scene and DNA Basics
- Laboratory Safety Programs
- DNA Amplification
- Population Genetics and Statistics
- Non-STR DNA Markers: SNPs, Y-STRs, LCN and mtDNA
- Firearms Examiner Training
- Forensic DNA Education for Law Enforcement Decisionmakers
- What Every Investigator and Evidence Technician Should Know About DNA Evidence
- Principles of Forensic DNA for Officers of the Court
- Law 101: Legal Guide for the Forensic Expert
- Laboratory Orientation and Testing of Body Fluids and Tissues
- DNA Extraction and Quantitation
- STR Data Analysis and Interpretation
- Communication Skills, Report Writing, and Courtroom Testimony
- Español for Law Enforcement
- Amplified DNA Product Separation for Forensic Analysts