DNA Extraction from Blood: Procedures and Quality Control

This article provides a working protocol for extracting high molecular weight DNA from whole blood, with quality control checkpoints at each stage. It is written for laboratory students, technicians, researchers, and diagnostic professionals who need a practical reference for routine extraction work. The procedures described cover cell lysis, protein digestion, purification, and the quality assessment methods of spectrophotometry and gel electrophoresis. The guidance emphasizes documentation, troubleshooting, and knowing when to escalate problems to a senior laboratory professional.

At a Glance

DNA extraction from blood follows a common sequence regardless of the specific kit or manual method used. The core steps are cell lysis, digestion of proteins, purification of nucleic acids, and elution into a stable buffer. Quality control is not a single event at the end of the protocol. It is a series of checks built into each stage, from the condition of the starting blood sample to the final spectrophotometric reading.

Core Principles of DNA Extraction from Blood

Nucleic acid isolation is the starting point for nearly all downstream molecular work, and the quality of the extracted DNA determines the reliability of every subsequent test. Successful extraction from whole blood requires four things to happen in sequence. The cellular and nuclear membranes must be disrupted, the nucleoprotein complexes must be denatured so that proteins separate from the DNA, nucleases must be inactivated before they can degrade the genetic material, and the DNA must be purified away from the other components of the blood sample. These steps can be adjusted depending on the nucleic acid of interest and the type of sample being processed. The same principles apply whether you are working with fresh venous blood, frozen samples, or dried blood spots on filter paper.

The choice of extraction method involves tradeoffs between yield, purity, cost, time, and the use of hazardous chemicals. Many published protocols and commercial kits produce acceptable results, but each has limitations. Some methods suffer from low yield, compromised quality, high cost, long processing times, or the need for toxic organic solvents. A laboratory with limited funding may need a protocol that avoids expensive reagents while still delivering DNA suitable for downstream applications. A rapid and economical method that avoids phenol and other toxic organic solvents can produce yields comparable to reference protocols and commercial kits, making it useful for basic molecular research in resource limited settings.

The condition of the starting blood sample is a major determinant of success. Fresh blood generally yields higher quality DNA than frozen blood, but frozen samples can still work well if they were stored properly and processed with an appropriate method. Blood frozen for extended periods, even up to several years, can yield DNA suitable for PCR, real time PCR, and Sanger sequencing when the extraction method is chosen carefully. The key is to match the extraction protocol to the condition of the sample and to verify the quality of the final product before proceeding to downstream applications.

Sample Collection and Storage Considerations

The anticoagulant used during blood collection affects downstream extraction. EDTA is the most common choice for DNA work because it chelates magnesium, which is a cofactor for many nucleases, and it does not interfere with PCR. Heparin should be avoided for molecular applications because it inhibits PCR even at low concentrations. Citrate is acceptable but may require adjustment of the lysis buffer volume.

Hemolysis is a visible indicator of sample quality. Red blood cells that have ruptured release hemoglobin and other proteins into the plasma, which can interfere with purification and reduce DNA yield. A hemolyzed sample is not necessarily unusable, but it requires a protocol that can handle the additional protein load. Coagulated blood presents a different challenge because the clot traps white blood cells and makes them difficult to access. Some protocols have been optimized specifically for hemolyzed and coagulated bovine blood, indicating that these sample types are common in veterinary and livestock diagnostics.

Storage duration and temperature are critical variables. Fresh blood processed within a few hours of collection gives the best results. If processing must be delayed, blood can be stored refrigerated for a short period or frozen for longer term storage. Freezing damages white blood cells and can release nucleases, so the freeze thaw cycle must be managed carefully. Blood frozen for two to three months and blood frozen for eighteen months have both been used successfully for DNA extraction, but the quality of the final product depends on the extraction method and the care taken during processing.

Dried blood spots are an alternative to liquid blood samples. They are less invasive to collect, require no cold chain for transport or storage, and are easier to handle in remote field settings. However, DNA yield from dried blood spots is generally lower than from fresh liquid blood. The membrane material itself can retain nucleic acids during the lysis stage, reducing the final yield. Glass fiber membranes tend to perform better than conventional cellulose filter paper, but even the best membrane results in some loss compared to a native sample. A short solubilization step before standard extraction can improve yield from dried samples.

Laboratory Safety and Biosafety Context

Working with human blood carries biological hazards. Blood may contain bloodborne pathogens, and all samples must be treated as potentially infectious regardless of the source. The World Health Organization Laboratory Biosafety Manual provides the international standard for safe handling of biological materials. Laboratory staff should follow institutional biosafety protocols, wear appropriate personal protective equipment, and perform all work with blood samples in a designated area that can be decontaminated.

The chemicals used in DNA extraction also require attention. Many traditional protocols use phenol and chloroform, which are toxic and must be handled in a fume hood with appropriate waste disposal. Some modern methods avoid these solvents entirely, using chaotropic salts and silica columns instead. A protocol that eliminates toxic organic solvents reduces occupational exposure and simplifies waste management. The choice of method should consider also the quality of the DNA produced but also the safety of the personnel performing the extraction.

Spills and accidents must be reported according to institutional policy. Needlestick injuries, splashes to the eyes or mucous membranes, and cuts from broken glass all require immediate first aid and follow up with occupational health services. The Laboratory Quality Management System Handbook from the World Health Organization emphasizes that quality in the laboratory depends on a safe working environment. A laboratory that cuts corners on safety will eventually compromise the quality of its results.

Step by Step DNA Extraction Protocol

The following protocol represents a general approach that can be adapted to the specific reagents and kits available in your laboratory. The volumes and times are starting points that should be optimized for your conditions. Record any deviations from the written protocol in your laboratory notebook.

Sample Preparation

Begin with 500 microliters of whole blood in a sterile microcentrifuge tube. If the blood was frozen, thaw it slowly on ice or at room temperature and mix gently by inversion. Do not vortex frozen blood vigorously, as this can shear the DNA from lysed cells. If you are working with a dried blood spot, cut a disc of the appropriate size and place it in a tube for processing.

Add the lysis buffer according to the manufacturer instructions or your validated protocol. The lysis buffer should contain a detergent to disrupt cell membranes and a chaotropic agent to denature proteins. Mix the sample thoroughly but gently. Incomplete mixing at this stage leads to clumps of unlysed cells that reduce yield.

Cell Lysis and Protein Digestion

Incubate the sample at the temperature specified for your lysis buffer. Most protocols use a temperature between 55 and 65 degrees Celsius. During this incubation, the detergent dissolves the cell membranes and the chaotropic salt denatures the proteins. The solution should become clear or slightly viscous as the cells break open.

Add proteinase K or a similar protease to digest the proteins that are bound to the DNA. The amount of enzyme and the digestion time depend on the specific product and the sample type. Blood samples with high white blood cell counts or samples that are hemolyzed may require more enzyme or a longer digestion time. Protein digestion is complete when the solution is homogeneous and no visible clumps remain.

Some protocols include an RNase digestion step to remove RNA from the preparation. This is important if the downstream application requires DNA free of RNA contamination. RNase is added after the proteinase K digestion and incubated briefly before the purification step.

DNA Purification

The method of purification depends on the protocol you are using. Silica column methods bind DNA to a membrane in the presence of a chaotropic salt, wash away contaminants, and elute the DNA in a low salt buffer or water. Organic extraction methods use phenol and chloroform to separate DNA into an aqueous phase, followed by alcohol precipitation.

For column based methods, apply the lysate to the column and centrifuge according to the manufacturer instructions. The DNA binds to the silica membrane while proteins, lipids, and other cellular debris pass through in the flow through. Wash the column with the provided buffers to remove residual contaminants. The final wash usually contains ethanol and must be removed completely before elution, because residual ethanol interferes with downstream applications.

For alcohol precipitation, add cold isopropanol or ethanol to the aqueous phase and mix gently. The DNA precipitates out of solution and can be collected by centrifugation. A visible white pellet should form. Wash the pellet with cold ethanol to remove residual salt, then allow the pellet to dry briefly. Do not over dry the pellet, as this makes the DNA difficult to resuspend. Resuspend the DNA in a buffered solution such as TE buffer instead of plain water, because the buffer maintains a stable pH and protects the DNA from degradation.

Elution and Storage

Elute the DNA in a volume appropriate for the expected yield and the downstream application. A smaller elution volume gives a higher concentration but may leave some DNA bound to the column. A larger volume gives a lower concentration but recovers more of the DNA. The choice depends on whether you need a high concentration for applications like Sanger sequencing or a moderate concentration for PCR.

Store the extracted DNA at the appropriate temperature. DNA in TE buffer is stable at 4 degrees Celsius for short term use and at minus 20 degrees Celsius or minus 80 degrees Celsius for long term storage. Repeated freeze thaw cycles should be avoided because they can shear the DNA. If you need to use the DNA multiple times, consider making aliquots so that each aliquot is thawed only once.

Quality Control Methods

Quality control is the process of verifying that the extracted DNA meets the standards required for downstream applications. Two methods are standard in most laboratories: spectrophotometry for quantity and purity, and gel electrophoresis for integrity and molecular weight.

Spectrophotometric Quantification and Purity Assessment

Spectrophotometry measures the absorbance of the DNA solution at specific wavelengths. DNA absorbs light most strongly at 260 nanometers, while proteins absorb most strongly at 280 nanometers. The ratio of absorbance at 260 to absorbance at 280, written as A260/A280, is the standard indicator of protein contamination. A pure DNA sample has an A260/A280 ratio of approximately 1.8 to 2.0. Lower ratios indicate protein contamination or the presence of other contaminants that absorb at 280 nanometers.

The A260/A230 ratio is a secondary measure of purity. It detects contamination by chaotropic salts, carbohydrates, and other compounds that absorb at 230 nanometers. A pure DNA sample should have an A260/A230 ratio above 1.5, with values around 2.0 being typical. Low A260/A230 ratios often indicate that the washing steps during purification were insufficient.

The concentration of DNA is calculated from the absorbance at 260 nanometers. An absorbance of 1.0 at 260 nanometers corresponds to approximately 50 micrograms per milliliter of double stranded DNA. This calculation assumes that the DNA is pure and that the spectrophotometer is properly calibrated. If the sample contains significant amounts of RNA or other contaminants, the concentration estimate will be inaccurate.

Spectrophotometric readings can be affected by the buffer used for elution. Some buffers contain compounds that absorb in the ultraviolet range and will inflate the absorbance readings. Always use the elution buffer as the blank for the spectrophotometer, and record the buffer type in your notes.

Gel Electrophoresis for DNA Integrity

Gel electrophoresis separates DNA fragments by size as they migrate through an agarose gel under an electric field. High molecular weight genomic DNA migrates slowly and appears as a single band near the top of the gel. Degraded DNA appears as a smear extending downward from the high molecular weight region, with smaller fragments migrating further into the gel. RNA contamination appears as a diffuse smear near the bottom of the gel or as distinct low molecular weight bands.

The gel is stained with a DNA binding dye and visualized under ultraviolet light or a blue light transilluminator. The intensity of the band can be compared to a molecular weight marker of known concentration to estimate the quantity of DNA in the sample. This visual estimate is less precise than spectrophotometry but provides information about DNA integrity that spectrophotometry cannot.

A high quality genomic DNA sample shows a single sharp band at high molecular weight with minimal smearing. Some laboratories use automated microchip electrophoresis platforms for this assessment. These systems provide a digital image of the gel and can calculate the size and concentration of the DNA fragments. They are particularly useful when many samples need to be assessed in a consistent manner.

Functional Quality Assessment

The ultimate test of DNA quality is whether it works in the downstream application. PCR amplification is a sensitive indicator of DNA quality because it requires the DNA to be free of inhibitors and intact enough to serve as a template. A sample that fails to amplify may have residual inhibitors from the extraction process, or the DNA may be too degraded to support amplification.

Restriction enzyme digestion is another functional test. Restriction enzymes recognize specific DNA sequences and cut the DNA at those sites. If the DNA is contaminated with proteins or other inhibitors, the restriction enzyme may not cut efficiently. A successful digestion indicates that the DNA is accessible to enzymes and free of inhibitors.

For applications like Sanger sequencing, the quality of the input DNA is crucial. Poor quality DNA produces poor quality sequence data, with weak signals, high background, or premature termination of the sequencing reaction. Laboratories that perform sequencing should verify the quality of their extracted DNA before submitting samples for sequencing.

Method Selection and Tradeoffs

The choice of DNA extraction method depends on the sample type, the downstream application, the available equipment, and the budget. No single method is best for every situation. Each method has strengths and weaknesses that must be weighed against the specific requirements of the work.

Manual Methods

Manual extraction methods are flexible and inexpensive. They can be modified to handle difficult samples, and the reagents are often cheaper than commercial kits. A manual method that uses a lower sodium chloride concentration for DNA precipitation and avoids phenol has been shown to provide the maximum DNA yield from stored blood samples. This modified method may be preferred for large scale applications because it provides a cost effective way to obtain large quantities of quality DNA.

The main disadvantage of manual methods is that they are labor intensive and require careful technique. Variability between operators can lead to inconsistent results. Manual methods also take more time than automated methods, which can be a limitation when processing large numbers of samples.

Commercial Kits

Commercial kits provide standardized reagents and protocols that are designed to work consistently. They are convenient and reduce the need for in house optimization. Many kits are available for DNA extraction from blood, and they differ in their performance characteristics.

The choice of kit can have a significant effect on DNA recovery. A comparison of five different extraction kits found large differences in DNA recovery between the kits, with the best performing kit demonstrating the highest recovery at low DNA amounts. This is particularly important for forensic samples, where the amount of DNA available is often limited.

Commercial kits are more expensive than manual methods on a per sample basis. The cost difference can be substantial when processing large numbers of samples. Some laboratories use manual methods for routine samples and reserve commercial kits for difficult samples or samples where the highest quality is required.

Automated Systems

Automated extraction systems process multiple samples simultaneously with minimal operator intervention. They are useful for laboratories with high sample throughput or for applications that require consistent results across many samples. Automated protocols are available for bacterial and fungal DNA extraction from blood samples, and these systems can process samples in a standardized manner.

The main disadvantage of automated systems is the initial capital cost. The instruments and the consumables are expensive, and the laboratory must have the volume of work to justify the investment. Automated systems also require regular maintenance and calibration to ensure consistent performance.

Magnetic Bead Methods

Magnetic bead methods use paramagnetic particles that bind DNA in the presence of a chaotropic salt. The beads are separated from the solution using a magnet, washed to remove contaminants, and the DNA is eluted in a low salt buffer. This approach is adaptable to automation and can handle complex sample matrices.

A magnetic bead method using guanidine isothiocyanate has been shown to yield high quantities of DNA with good purity from blood samples. The processing time was shorter than a commercial kit, and the method did not require toxic reagents such as phenol or chloroform. The DNA yield was 20 to 30 percent higher than that of commercial kits, and the method demonstrated strong tolerance to coexisting contaminants.

Records and Measurements

Accurate record keeping is essential for quality control in the diagnostic laboratory. The World Health Organization Laboratory Quality Management System Handbook emphasizes that documentation is a core component of laboratory quality. Every extraction run should be documented with sufficient detail that another qualified person could repeat the work and understand the results.

Essential Records for Each Extraction Run

Record the date and time of the extraction, the identity of the operator, and the unique identifier of each sample. Note the type of blood sample, the anticoagulant used, and the storage conditions and duration before processing. Record the extraction method, including the specific kit or manual protocol, the lot numbers of all reagents, and any deviations from the written protocol.

Record the quality control results for each sample. This includes the spectrophotometric readings, the A260/A280 and A260/A230 ratios, the calculated DNA concentration, and the gel electrophoresis results. Note any observations about the appearance of the sample, such as hemolysis, clotting, or unusual viscosity.

Record the downstream application and the date it was performed. If the DNA was used for PCR, note the target gene and the result. If the DNA was used for sequencing, note the quality of the sequence data. This information allows you to correlate extraction quality with downstream performance.

Interpreting Quality Control Results

The interpretation of quality control results requires context. A DNA sample with an A260/A280 ratio of 1.7 may be perfectly acceptable for PCR but may not be suitable for applications that require very high purity. The acceptable ranges depend on the downstream application and the requirements of the specific test.

A low A260/A280 ratio indicates protein contamination. This can often be corrected by repeating the purification step or by increasing the proteinase K digestion time. A low A260/A230 ratio indicates salt or carbohydrate contamination, which is often caused by incomplete washing during purification. This can be corrected by repeating the wash steps or by precipitating the DNA again.

Gel electrophoresis results should be interpreted in the context of the sample type. DNA from frozen blood may show some degradation even with careful handling, and a small amount of smearing may be acceptable. DNA from dried blood spots is often partially degraded due to the storage conditions. The key question is whether the DNA is intact enough for the intended downstream application.

Common Failure Patterns and Troubleshooting

Understanding the common failure patterns in DNA extraction helps you diagnose problems quickly and take corrective action. The following are the most frequently encountered issues and their likely causes.

Low DNA Yield

Low yield is one of the most common problems in DNA extraction. The cause may be in the starting sample, the extraction procedure, or the quantification method. A blood sample with a low white blood cell count will yield less DNA than a sample with a normal count. This is expected and does not indicate a problem with the extraction.

Incomplete cell lysis reduces yield because DNA remains trapped in unlysed cells. This can be caused by insufficient lysis buffer, inadequate mixing, or an incubation temperature that is too low. Increasing the lysis buffer volume or extending the incubation time can improve lysis.

DNA loss during purification is another common cause of low yield. DNA can be lost during the washing steps, particularly if the wash buffer is too warm or if the centrifugation conditions are incorrect. DNA can also remain bound to the purification column if the elution volume is too small or if the elution buffer is not at the correct pH.

Protein Contamination

Protein contamination is indicated by a low A260/A280 ratio. The most common cause is incomplete protein digestion. Proteinase K requires sufficient time and the correct temperature to work effectively. If the digestion time is too short or the temperature is too low, proteins remain bound to the DNA.

Protein contamination can also result from carryover of the organic phase during phenol chloroform extraction. Care must be taken to remove only the aqueous phase without disturbing the interface. If the interface is disturbed, proteins can contaminate the DNA.

DNA Degradation

DNA degradation appears as smearing on a gel, with the DNA extending from the high molecular weight region down to lower molecular weights. The most common cause is nuclease activity. Nucleases can be introduced from the blood sample itself, from contaminated reagents, or from the hands of the operator. Gloves should be worn at all times, and reagents should be certified nuclease free.

Repeated freeze thaw cycles can also degrade DNA. Each freeze thaw cycle causes physical damage to the DNA molecule. Aliquoting the DNA into smaller volumes reduces the number of freeze thaw cycles.

PCR Inhibition

PCR inhibition is indicated by a failure to amplify or by weak amplification when the DNA concentration appears adequate. Inhibitors can be carried over from the blood sample, such as hemoglobin, or introduced during the extraction process, such as residual ethanol or chaotropic salts.

Residual ethanol is a common cause of PCR inhibition. Ethanol is used in the washing steps of many extraction protocols, and it must be completely removed before elution. If the DNA pellet or column is not dried sufficiently, ethanol carries over into the eluate.

Hemoglobin is a potent inhibitor of PCR. Blood samples that are hemolyzed contain more free hemoglobin, which can be difficult to remove completely. Some extraction methods are better than others at removing hemoglobin, and the choice of method may need to be adjusted for hemolyzed samples.

Professional Escalation Criteria

Knowing when to escalate a problem to a senior laboratory professional is an important skill. Some problems can be solved by adjusting the protocol, but others indicate a more serious issue that requires expert intervention.

Escalate to a senior laboratory professional if you observe any of the following:

• Repeated failure of the quality control checks despite troubleshooting. If multiple extraction runs produce DNA with poor purity ratios or visible degradation, the problem may be in the reagents, the equipment, or the protocol itself.
• Unexpected results in downstream applications. If PCR amplification fails repeatedly with DNA that appears to be of good quality, there may be an inhibitor that is not detected by routine quality control.
• Contamination of reagents or equipment. If you suspect that a reagent is contaminated or that the equipment is not functioning correctly, stop work and report the issue.
• Any deviation from the validated protocol that produces unexpected results. If you modified the protocol to handle a difficult sample and the results are not acceptable, a senior professional may be able to suggest an alternative approach.
• Results that are inconsistent with the clinical picture or that cannot be explained by the available data. In a diagnostic setting, unexpected results must be investigated before they are reported.

The World Health Organization Laboratory Quality Management System Handbook provides guidance on the management of nonconforming work. When a quality control failure occurs, the laboratory should have a procedure for documenting the issue, investigating the cause, and taking corrective action. This process should be followed consistently to maintain the quality of the laboratory's results.

Limitations of DNA Extraction and Quality Control

DNA extraction and quality control have inherent limitations that must be understood to interpret results correctly. No extraction method recovers all of the DNA from a blood sample. Some DNA is always lost during the purification process, and the yield is always lower than the theoretical maximum.

The quality control methods themselves have limitations. Spectrophotometry measures the average absorbance of the entire sample, so it cannot detect localized contamination or degradation. A sample with a good A260/A280 ratio may still contain inhibitors that affect PCR. Gel electrophoresis provides a visual assessment of DNA integrity, but it is not quantitative unless a standard curve is used.

The condition of the starting sample imposes limits on the quality of the extracted DNA. DNA from frozen blood is never as intact as DNA from fresh blood, regardless of the extraction method. DNA from dried blood spots is always partially degraded and is present in lower quantities than from liquid blood. These limitations must be considered when interpreting results and when designing experiments.

The choice of extraction method can also limit the downstream applications. Some methods produce DNA that is suitable for PCR but not for applications that require very high molecular weight DNA, such as long range PCR or certain sequencing approaches. The method should be chosen based on the requirements of the downstream application.

Frequently Asked Questions

What is the best anticoagulant for blood samples intended for DNA extraction?

EDTA is the preferred anticoagulant for DNA extraction because it chelates magnesium ions that are required by nucleases, helping to protect the DNA from degradation. EDTA does not interfere with PCR. Heparin should be avoided because it inhibits PCR even at low concentrations. Citrate is acceptable but may require adjustment of the lysis buffer volume.

How long can blood be stored before DNA extraction?

Fresh blood processed within a few hours of collection gives the best results. If processing must be delayed, blood can be stored refrigerated for a short period or frozen for longer term storage. Blood frozen for two to three months and blood frozen for eighteen months have both been used successfully for DNA extraction. The quality of the final product depends on the extraction method and the care taken during processing.

What does the A260/A280 ratio indicate?

The A260/A280 ratio indicates protein contamination in the DNA sample. A pure DNA sample has a ratio of approximately 1.8 to 2.0. Lower ratios indicate protein contamination or the presence of other contaminants that absorb at 280 nanometers. The ratio should be interpreted in the context of the downstream application, as some applications tolerate lower purity than others.

Why is my DNA yield lower than expected?

Low yield can result from a low white blood cell count in the starting sample, incomplete cell lysis, DNA loss during purification, or incomplete elution. Check the lysis step for complete cell breakage, verify that the wash steps are performed correctly, and confirm that the elution volume and buffer are appropriate. The yield from dried blood spots is generally lower than from liquid blood due to retention of nucleic acids by the membrane material.

What causes DNA degradation during extraction?

DNA degradation is most commonly caused by nuclease activity. Nucleases can come from the blood sample itself, from contaminated reagents, or from the hands of the operator. Repeated freeze thaw cycles can also degrade DNA. Use nuclease free reagents, wear gloves, and aliquot the DNA to minimize freeze thaw cycles.

Can I use DNA extracted from frozen blood for sequencing?

Yes, DNA extracted from frozen blood can be used for sequencing if the extraction method is chosen carefully. Blood frozen for up to three years has been used successfully for Sanger sequencing. The quality of the input DNA is crucial for obtaining significant results from sequencing, so the extracted DNA should be assessed for quality before proceeding.

What is the difference between A260/A280 and A260/A230 ratios?

The A260/A280 ratio detects protein contamination, while the A260/A230 ratio detects contamination by chaotropic salts, carbohydrates, and other compounds that absorb at 230 nanometers. A pure DNA sample should have an A260/A280 ratio of approximately 1.8 to 2.0 and an A260/A230 ratio above 1.5. Low A260/A230 ratios often indicate that the washing steps during purification were insufficient.

How do I choose between a manual method and a commercial kit?

The choice depends on your sample type, downstream application, budget, and available equipment. Manual methods are flexible and inexpensive but require careful technique and are labor intensive. Commercial kits are convenient and standardized but cost more per sample. Some laboratories use manual methods for routine samples and reserve commercial kits for difficult samples or samples where the highest quality is required.

Related Diagnostic Guides

• Plasmid DNA Purification Using Alkaline Lysis: Miniprep Protocol and Quality Control
• Agarose Gel Electrophoresis for DNA Analysis: Protocol and Troubleshooting
• Procedure for Quality Control: Step-by-Step Implementation in a Molecular Lab
• Gel Electrophoresis Quality Control: Assessing DNA Integrity and Purity
• Restriction Digestion of Plasmid DNA: Protocol, Troubleshooting, and Quality Checks

References and Further Reading

• Laboratory Quality Management System Handbook. World Health Organization.
• Laboratory Biosafety Manual. World Health Organization.
• Assay Guidance Manual. National Center for Advancing Translational Sciences.
• Bioanalytical Method Validation Guidance. U.S. Food and Drug Administration.
• NCBI Literature Resources. National Center for Biotechnology Information.
• A rapid and efficient DNA extraction protocol from fresh and frozen human blood samples.. Journal of clinical laboratory analysis, 2018.
• A simplified universal genomic DNA extraction protocol suitable for PCR.. Genetics and molecular research : GMR, 2011.
• Nucleic Acid Extraction from Human Biological Samples.. Methods in molecular biology (Clifton, N.J.), 2019.
• Amplification-refractory mutation system (ARMS) analysis of point mutations.. Current protocols in human genetics, 2001.
• Optimized Protocol For DNA Extraction from Human Whole Blood.. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology, 2025.
• Preservation and Extraction of Malaria Parasite DNA from Dried Blood Spots.. Methods in molecular biology (Clifton, N.J.), 2022.
• Optimization of Total DNA Extraction from Dried Blood Samples.. Biochemical genetics, 2025.
• Functional assessment of DNA extraction methods from frozen human blood samples for Sanger sequencing analysis.. Cellular and molecular biology (Noisy-le-Grand, France), 2023.
• DNA Recovery Using Different Extraction Kits and Cotton Swabs in Forensic DNA Analysis.. 2026.
• ABO and Amelogenin Determination by PCR, from Experimental Bloodstains and from Museum Specimens, Using a Non-Destructive Approach. 2026.
• Improved DNA Extraction for Dairy and Blood Products: A Comparative Evaluation of Yield, Purity, and PCR Compatibility.. 2026.
• Preliminary Comparison of a Modified cfDNA Extraction Protocol for Y-Chromosome Marker Detection in Maternal Plasma. 2026.
• Advancing diagnostics for Chagas disease: key product characteristics and harmonized evaluation strategies - an expert meeting report.. 2026.
• Genomic DNA Quality Assessment by an Automated Microchip Electrophoresis Platform.. 2013.
• DNA quality assessment and amplification for array CGH. 2007.
• Second SPIDIA-DNA External Quality Assessment (EQA): Influence of pre-analytical phase of blood samples on genomic DNA quality.. Clinica chimica acta, international journal of clinical chemistry, 2016.
• Comparative environmental RNA and DNA metabarcoding analysis of river algae and arthropods for ecological surveys and water quality assessment. Scientific Reports, 2022.
• Urinary Cell-Free DNA: Isolation, Quantification, and Quality Assessment.. Methods in molecular biology, 2019.
• International pilot external quality assessment scheme for analysis and reporting of circulating tumour DNA. BMC Cancer, 2018.
• Optimization of a DNA extraction protocol for hemolyzed and coagulated bovine blood for use in molecular detection of Anaplasma spp.. Revista Mexicana De Ciencias Pecuarias, 2021.
• A novel, efficient, fast and inexpensive DNA extraction protocol from whole blood applicable for studying drug-DNA interaction. Journal of Reports in Pharmaceutical Sciences, 2014.
• A comparison of DNA extraction protocols from blood spotted on FTA cards for the detection of tick-borne pathogens by Reverse Line Blot hybridization. Ticks and Tick Borne Diseases, 2017.
• Bacterial and fungal dna extraction from blood samples: Automated protocols. Methods in Molecular Biology, 2014.
• A comparative evaluation of four DNA extraction protocols from whole blood sample. Cellular and Molecular Biology, 2016.

This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.