Updated on: October 1, 2020

What is DNA?

DNA, which is short for deoxyribonucleic acid, is the hereditary material that is passed to humans from parents and other ancestors. Nearly every cell in your body has the same DNA, which almost all of it is stored in the cell’s nucleus. A bit of DNA is also found in the mitochondria, which is why it is called mitochondrial DNA or mtDNA.

DNA is valuable because it contains information. This information stores code featuring four chemical bases:

  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T)

Your DNA contains approximately 3 billion bases. A person’s DNA code gives a great deal of identifying information about that person through DNA analysis.

What is DNA Analysis? 1

What is DNA analysis?

DNA analysis came into use in the 1980s when Alec Jeffreys, an English geneticist, discovered how to “unlock” DNA code and use it to identify individuals within a species. DNA analysis isn’t perfect and presents special challenges when it’s being used to identify someone from someone else. For example, you can easily use DNA evidence to determine if someone was attacked by a mountain lion or a man. But identifying which man or which mountain lion did the attacking is another story.

How do you use DNA?

There are several ways to use DNA analysis. It’s gotten a lot of attention for its role as evidence in the criminal justice system, but there are other uses. It is one of the most accurate methods available for identifying someone and when it became legal and possible to use DNA evidence in criminal cases, it turned the judicial system upside down.

DNA is also used to identify victims or their remains and to evaluate a person’s risk of genetic diseases.

What’s the Difference between DNA Sequencing and DNA Profiling?

DNA sequencing and DNA profiling are terms sometimes used interchangeably. However, they don’t mean the same thing even though there is a relation.

DNA profiling is a forensic technique. A DNA sample is evaluated and used to identify an individual. On the other hand, DNA sequencing is a technique used in the biotech industry that determines the nucleic acid sequence of a particular DNA fragment.

The actual processes of sequencing and profiling are different, too. Profiling occurs in the STR analysis by PCR and gel electrophoresis. Sequencing occurs in the incorporation of labeled dideoxynucleotides by PCR and the determination of nucleotide sequence by gel electrophoresis. Molecular biology uses both, which provides valuable information about a person’s biological identity.

What Type of DNA Sample Method IS Used and What Are the Different Types of DNA Available for Testing?

There are two techniques used for sampling, including:

  •  Restriction fragment length polymorphism (RFLP)
  • Polymerase chain reaction (PCR)

The size of the sample determines which of these two methods will work best.

Sources of DNA Evidence

You collect DNA samples in a variety of different ways, but only three sources are used in DNA analysis:

  • Subject
  • Subject’s relatives
  • Other people

Samples from any of these three sources can provide information about a situation involving DNA. These sources confirm or deny a connection to a particular situation.

From the sources listed above, you collect samples in one of several ways, including:

  • Sweat
  • Skin
  • Blood
  • Tissue
  • Hair
  • Dandruff
  • Mucus
  • Semen
  • Ear wax
  • Saliva
  • Vaginal or rectal cells

Investigators collect samples from a variety of places, including directly from the subject, from items he or she has touched, or from a sample “left behind,” such as a hair that fell out.

What is DNA Analysis? 2

What is the future of Forensic DNA Testing?

People who study DNA predict a variety of developments in the future. These predictions include:

  • Use of a procedure called “Short Tandem Repeats” will increase in the next 10 years
  • It will be possible to analyze DNA at a crime scene and get immediate identification using miniature chips that access databases
  • mDNA will be used more in difficult cases that involve very small amounts of DNA or old/degraded DNA samples
  • DNA databases with profiles of convicted felons will grow and state-to-state and international comparisons will become common
  • A conventional method will be developed that allows for scientifically unreliable matches to be used for legal and social identification
  • More suspects will be identified via database searches

Considerations When Evaluating DNA Evidence

With all the benefits that come with using DNA evidence, there are also pitfalls.

DNA isn’t perfect, though it’s closer to perfect than many other types of evidence. However, human error or bias corrupts the analysis of DNA evidence. This could result in linking innocent people to crimes and pointing to “airtight” evidence as proof when it’s not completely reliable.

Privacy concerns also exist. Conducting familial searches exposes people not connected to criminal activity and pulls them into a situation. It might even expose family connections people didn’t know existed.

Finally, racial disparities exist when it comes to DNA analysis. Because more African American men have their DNA stored in state and federal databases, there is a higher risk of surveillance on minority communities.

Overall, there is a concern that DNA analysis could lead to the creation of a “genetic dragnet,” and bring people with no direct link to crime into an investigation, exposing their privacy for no reason.

Joel is a writer with a passion for the science of DNA and the power of its manipulation.
Resources

Genetics Home Reference. “What Is DNA?” Genetics Home Reference, 2019, ghr.nlm.nih.gov/primer/basics/dna.

“Future of Forensic DNA Testing: Predictions of the Research and Development Working Group.” National Institute of Justice, nij.ojp.gov/library/publications/future-forensic-dna-testing-predictions-research-and-development-working-group

“DNA Evidence: Basics of Identifying, Gathering and Transporting.” National Institute of Justice, 2012, nij.ojp.gov/topics/articles/dna-evidence-basics-identifying-gathering-and-transporting.

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