Human Genetics 4th Semester

2. DNA EXTRACTION

3. DNA EXTRACTION
• You’ve probably heard of the Genetic Code or the Blueprint of Life; these terms
refer to DNA. All living things, including animals, plants, and bacteria, have DNA
in their cells. DNA is a very long molecule made up of a chain of nucleotides and
the order of these nucleotides is what makes organisms similar to others of their
species and yet different as individuals.

4. • in order to study DNA, you first have to get it out of the cell. In eukaryotic cells,
such as human and plant cells, DNA is organized as chromosomes in an organelle
called the nucleus. Bacterial cells have no nucleus. Their DNA is organized in rings
or circular plasmids, which are in the cytoplasm. The DNA extraction process frees
DNA from the cell and then separates it from cellular fluid and proteins so you
are left with pure DNA.

5. • Genes are sections within this long DNA molecule DNA is extracted from human
cells for a variety of reasons. With a pure sample of DNA you can test
• a newborn for a genetic disease,
• analyze forensic evidence, or
• study a gene involved in cancer…………….

6. ISOLATION OF DNA
• Scientist isolated DNA for a variety of reason ,some of which include
• Body Identification
• Genetic Testing
• Analysis of Forensic Evidence .
• That's more than enough to provide a profile that accurately identifies a person. DNA is
often left behind at a crime scene. It is present in all kinds of evidence, including blood, hair,
skin, saliva, and semen. Scientists can analyze the DNA in evidence samples to see if it
matches a suspect's DNA.

7. GENETIC SIGNATURE
• Most genetic ancestry tests involve the analysis of small snippets of DNA passed
down only through the mother, or only through the father. These tests can
identify related individuals who share a common maternal or paternal ancestor,
and even where in the world people with your genetic signature live today.
• A gene signature or gene expression signature is a single or combined group
of genes in a cell with a uniquely characteristic pattern of gene expression.

8. WHY DNA EXTRACTION IS FIRST STEP?
• DNA extraction is typically the first step in a longer Laboratory process.
• DNA extraction is an important part of the process because the DNA first needs
to be purified away from proteins and other cellular contamination.
• We need cells ,because that’s where the DNA is?
• Inside almost every cells in our bodies is a nucleus ,and inside each nucleus is about
two meter of DNA .

10. COLLECTION OF CELLS:
The Skin on the inside of our mouths loses thousands of cells every day.

12. STEPS
• Collect cheek cells.
• Burst cells open to release DNA. ( Lysis)
• Separate DNA from Protein and Debris. (Precipitation)
• Isolation of concentrated DNA. (Purification)

13. THE THREE BASIC STEPS OF DNA EXTRACTION ARE
• 1. Lysis,
• 2. Precipitation,
• 3. Purification.

14. STEP 1: LYSIS
In this step, the cell and the nucleus are broken open to release the DNA inside and there are
two ways to do this.
First, mechanical disruption breaks open the cells. This can be done with a tissue homogenizer
(like a small blender), with a mortar and pestle, or by cutting the tissue into small pieces.
Mechanical disruption is particularly important when using plant cells because they have a tough
cell wall.
Second, lysis uses detergents and enzymes such as Proteinase K to free the DNA and dissolve
cellular proteins.

15. STEP 2: PRECIPITATION
When you complete the lysis step, the DNA has been freed from the nucleus, but
it is now mixed with mashed up cell parts.
Precipitation separates DNA from this cellular debris. First, Na+ ions (sodium)
neutralize the negative charges on the DNA molecules, which makes them more
stable and less water soluble. Next, alcohol (such as ethanol or isopropanol) is
added and causes the DNA to precipitate out of the aqueous solution because it
is not soluble in alcohol.

16. STEP 3: PURIFICATION
Now that DNA has been separated from the aqueous phase, it can be rinsed with
alcohol to remove any remaining unwanted material and cellular debris. At this
point the purified DNA is usually re-dissolved in water for easy handling and
storage.

17. MATERIAL USED IN DNA EXTRACTION
• Centrifuge machine
• Warm Water bath
• Micropipettes
• Buccal swab
• Sample tubes (Eppendorf)
• Tips
Reagent used in DNA extraction:
Lysis Solution
Concentrated Salt Solution
Suspension Buffer
Ethanol
Iso propyl Alcohol

18. LYSIS SOLUTION
• Lysis solution contain two important ingredients
• Detergent
• Proteinase K
The detergent disrupts the cell membrane and nuclear enveloped causing the cell to
burst open and release their DNA.
The DNA is still wrapped very tightly around protein called histones , and the proteinase
K outs a part the histones to free the DNA.

19. • Salt Solution :
The Salt Causes proteins and other cellular debris to clump together.
• Isopropyl alcohol: dissolves a wide range of non-polar compounds. It also
evaporates quickly, leaves nearly zero oil traces, compared to ethanol, and is
relatively non-toxic, compared to alternative solvents. Thus, it is used widely as a
solvent and as a cleaning fluid, especially for dissolving oils.

21. GET READY TP PRFORM
• https://learn.genetics.utah.edu/content/labs/extraction/