Extraction of DNA

Extraction of DNA from blood is a common laboratory procedure used in various scientific and medical applications, including genetic testing, forensic analysis, and research studies. Here's a general overview of the process:

Materials and Equipment:

• Blood sample (collected in EDTA tubes to prevent clotting)
• Lysis buffer (containing detergents and salts to disrupt cell membranes)
• Proteinase K (enzyme that digests proteins)
• Phenol-chloroform-isoamyl alcohol (PCI) solution (for organic extraction of DNA)
• Ethanol (for DNA precipitation)
• Spin columns or centrifuge tubes (for DNA purification)
• Microcentrifuge
• Pipettes and tips
• Microcentrifuge tubes
• Water bath or heat block (for incubation)

Procedure:

1. Lysis of Blood Cells:

• Transfer the blood sample to a microcentrifuge tube.
• Add an appropriate volume of lysis buffer to the tube, ensuring thorough mixing to lyse the blood cells and release the DNA.
• Optionally, add proteinase K to the lysis buffer to digest proteins and remove contaminants.

1. Incubation:

   • Incubate the sample at an appropriate temperature (typically 55-65°C) for a specified duration (e.g., 1-2 hours) to facilitate cell lysis and DNA release. Alternatively, overnight incubation may be performed for improved DNA yield.
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2. Organic Extraction:

• Add an equal volume of PCI solution to the lysed sample.
• Mix the solution thoroughly by inversion or vortexing to ensure proper phase separation.
• Centrifuge the sample at high speed (e.g., 10,000-15,000 × g) for several minutes to separate the aqueous and organic phases.

1. DNA Precipitation:

• Transfer the aqueous (upper) phase containing the DNA to a clean microcentrifuge tube.
• Add an equal volume of cold ethanol to the tube and mix gently by inversion to precipitate the DNA.
• Centrifuge the tube at high speed to pellet the DNA.

1. Washing and Purification:

• Remove the supernatant carefully without disturbing the DNA pellet.
• Wash the DNA pellet with cold ethanol to remove residual contaminants.
• Air-dry the DNA pellet briefly or use a microcentrifuge to remove excess ethanol.
• Resuspend the DNA pellet in an appropriate buffer or elution solution.

1. Quantification and Storage:

• Measure the concentration and purity of the extracted DNA using spectrophotometry or fluorometry.
• Store the DNA at -20°C or -80°C for long-term preservation, or proceed with downstream applications such as PCR, sequencing, or genotyping.

This is a basic outline of the DNA extraction process from blood. Variations of this protocol may be employed depending on the specific requirements of the experiment or application. Additionally, commercial DNA extraction kits are available, which provide standardized protocols and reagents for efficient DNA isolation from blood samples.