What is the Difference Between DNA Profiling and DNA Sequencing

The main difference between DNA profiling and DNA sequencing is that DNA profiling is the forensic technique, which allows the identification of individuals according to their genetic makeup whereas DNA sequencing is the technique in biotechnology, determining the nucleic acid sequence of a particular DNA fragment. Furthermore, DNA profiling takes part in the STR analysis by PCR and gel electrophoresis while DNA sequencing takes part in the incorporation of labeled dideoxynucleotides by PCR and the determination of nucleotide sequence by gel electrophoresis. 

DNA profiling and DNA sequencing are two techniques in molecular biology. Generally, they provide information about the genome of an individual. 

Key Areas Covered 

1. What is DNA Profiling
     – Definition, Procedure, Importance
2. What is DNA Sequencing
     – Definition, Procedure, Importance
3. What are the Similarities Between DNA Profiling and DNA Sequencing
     – Outline of Common Features
4. What is the Difference Between DNA Profiling and DNA Sequencing
     – Comparison of Key Differences

Key Terms 

DNA Profiling, DNA Sequencing, Forensic Identification, Nucleotide Sequence, Parentage Testing, STRs

What is DNA Profiling 

DNA profiling or genetic profiling is the forensic technique important in the identification of individuals and for parentage testing. Significantly, this method was developed by Sir Alec Jeffreys in conjunction with Peter Gill and Dave Werrett of the Forensic Science Service (FSS).

Figure 1: DNA Profiles

Generally, DNA profiling plays a key role in the comparison of DNA profiles of the criminal suspects. Also, it is a simple process, which is more statistically straightforward due to automation. 

Procedure 

DNA profiling focuses on using a panel of multi-allelic STR markers, which are structurally analogous to the original minisatellites. Generally, STRs are much shorter in comparison to the minisatellites; usually, they are the repeats of four bases. Therefore, it is easier to amplify them with multiplex PCR. Meanwhile, they can be amplified by using sequence-specific primers. Following, either gel electrophoresis or capillary electrophoresis takes part in the separation of the resulting fragments.

Figure 2: DNA Profiling

Remarkably, up to 30 STRs can be analyzed in a single capillary electrophoresis injection. For instance, STRs are highly polymorphic regions. However, the number of STR alleles in the human population is very small. Normally, similar STR alleles occur around 5-20% of individuals. 

What is DNA Sequencing 

DNA sequencing is the molecular biology technique important for the determination of the nucleotide base sequence. Generally, the first more rapid DNA sequencing method was developed by Frederick Sanger in 1977. Also, the method was known as ‘DNA sequencing with chain-terminating inhibitors’. However, another DNA sequencing method was developed by Walter Gilbert and Allan Maxam in 1973. For instance, this method was known as ‘DNA sequencing by chemical degradation’. Usually, both methods were identified as first-generation DNA sequencing methods.

Figure 3: DNA Sequencing

Moreover, high-throughput sequencing methods called ‘Next-generation sequencing’ or ‘second-generation sequencing methods were developed in the mid to late 1990s. Significantly, these methods allowed the ‘massive parallel’ sequencing through the automation of the process. Importantly, they allow the sequencing of whole genomes at once. 

Procedure 

Typically, Sanger sequencing divides DNA sample into four separate sequencing reactions, allowing the addition of four dideoxynucleotides (ddATP, ddCTP, ddGTP, and ddTTP) into each reaction mixture separately. Here, each dideoxynucleotide is fluorescently labeled (ddATP with green dye, ddCTP with blue dye, ddGTP with yellow dye, and ddTTP with red dye). Also, their concentration is approximately 100-fold lower than that of the deoxynucleotide.  

Figure 4: Sanger Sequencing

Basically, after undergoing polymerase chain reaction, amplicons after heat denaturation are size-fractionated on a denaturing polyacrylamide-urea gel. Ultimately, the nucleotide sequence can be determined through the visualization of the gel. 

Similarities Between DNA Profiling and DNA Sequencing 

• DNA profiling and DNA sequencing are two techniques in molecular biology. 
• Both help to reveal the nucleotide sequence of the genome. 
• Commonly, they use PCR and gel electrophoresis during their procedures.  
• Similarly, both techniques have numerous applications in forensic identifications and paternity testing. 

Difference Between DNA Profiling and DNA Sequencing 

Definition 

DNA profiling refers to the analysis of unique patterns of DNA sequences in the genome in order to identify individuals, while DNA sequencing refers to the determination of the nucleotide sequences of a DNA fragment. 

Focused Elements 

DNA profiling focuses on STR patterns of a particular locus while DNA sequencing focuses on the nucleotide sequence of a DNA fragment. 

Purpose of PCR 

PCR is responsible for the amplification of STR regions through sequence-specific priming in DNA profiling. In contrast, in DNA sequencing, PCR is responsible for the incorporation of labeled dideoxynucleotides to the amplicons. 

Importance 

DNA profiling is important in the identification of individuals in forensic studies as well as parentage testing while DNA sequencing is important to study genomes and proteomes, identification of new alleles, etc. 

Conclusion 

Basically, DNA profiling is the technique widely applicable in forensic studies for the identification of individuals depending on their genetic makeup. Generally, it uses STR patterns of a particular locus for the purpose. On the other hand, DNA sequencing is a technique in molecular biology, revealing the nucleotide sequence of a particular DNA fragment. Basically, it is important for studying genomes, the identification of new alleles, etc. Therefore, the main difference between DNA profiling and DNA sequencing is their procedure and importance. 

References:

1. Cornell, Brent. “DNA Profiling.” BioNinja, Available Here.
2. Adams, J. (2008) DNA sequencing technologies. Nature Education 1(1):193, Available Here. 

Image Courtesy:

1. “CBP chemist reads a DNA profile” By James Tourtellotte, photo editor of CBP Today (Public Domain) via Commons Wikimedia   
2. “Stages of Gene Fingerprinting” By Sneptunebear16 – Own work (CC BY-SA 4.0) via Commons Wikimedia    
3. “Radioactive Fluorescent Seq” By Abizar at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia    
4. “Sanger-sequencing” By Estevezj – Own work (CC BY-SA 3.0) via Commons Wikimedia