Forensic Biotechnology - PowerPoint Presentation

Slide1

Forensic

Biotechnology

T.A.

Roba Attar

DNA Extraction from Blood

What is DNA?

Deoxyribonucleic Acid is a very long molecule that carries genetic information that governs a person's physical characteristics. Each individual inherits half their DNA from their mother and the other half from their father. With the exception of identical twins, no two individuals share the same DNA sequence. DNA is found in the nucleus of every cell in the body except red blood cells have no nucleus and therefore no DNA.

There are many regions of DNA molecules that do not hold any known genetic information, but that vary enormously from person to person.

These are called non-coding or 'junk' DNA, and are used by forensic scientists to distinguish between individuals. Junk DNA cannot be used to build up a physical picture of an individual, or identify race or age.

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Because forensic scientists do not look at the whole of a person's DNA sequence, but rather a set of characteristics in non-coding DNA, the results are called a DNA profile. DNA profiles are a very powerful means of determining whether two samples may or may not have come from the same person. If two DNA profiles do not match, they must have come from two separate individuals. However, if they do match, there is only a small chance that they come from two different people.

DNA - the modern forensic investigative tool

Because DNA is the same in all cells of the body, DNA profiles extracted from different types of samples at different times and in different places can be compared to determine whether they may have come from the same person. Therefore, if human biological samples are found at a crime scene, DNA profiling can be used to determine whether a suspect could be a possible source of a sample.

Possible examples

A sexual assault case where the offender has left semen on the victim's clothing. The DNA profile from the semen could be compared with a blood or saliva sample from a suspect. A burglary where the offender has suffered a cut when breaking a window to gain entry. The DNA profile from blood stains on the broken window could be compared with a blood or saliva sample from a suspect. 

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A murder where the victim has suffered multiple stab wounds and a suspect is subsequently apprehended in possession of blood stained clothing. The DNA profile from the blood stained clothing could be compared with a sample from the victim.Sufficient quantities of DNA for profiling can be extracted from traces of human biological material such as blood, semen, sweat, hair and saliva.

Extraction of DNA

Before a DNA profile can be prepared from a human sample the DNA must be isolated from other organic and non-organic components of the sample. The type of sample will determine the particular isolation technique used. Isolation techniques may involve the use of enzymes to break down proteins and other cellular material.chelating agents to ensure that non-organic material does not degrade the

DNA.

organic solvents to separate the DNA from the other organic and non-organic material where necessary.

Once the DNA has been extracted from the sample, a number of different techniques can be used to develop a DNA profile. Techniques for developing profiles are constantly improving or being superseded.

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DNA extraction from Blood

Materials:Distilled waterGlovesSyringes 10 ml each (without needle)Beakers Table spoonPaper filter / coffee filter paperIsopropanolBlood sampleSodium Chloride / or Table salt

Procedure

Get the beaker and add 45 ml of water to it + then add 5 ml of the (dish soap) detergent + and then add 1 table spoon of salt and mix them all together with the spoon. (solution)Add few drops of the blood sample to the above solution. ( mix them all together)Filter the blood solution by using coffee filter paper and wait until all the solution is filtered.Take 10 ml of the blood solution that has been filtered by using syringe and put it in a small beaker. Then, add to that: 10 ml of isopropanol.Finally, we can see the DNA clearly visible in the supernatant layer at the top.

Why do we add detergents as part of the solution of the DNA Blood extraction procedure?

The DNA is held inside the nucleus of the cells we are using (white blood cells) but the red blood cells do not contain DNA. To free the DNA, it will be necessary to breakdown the membranes of the cells as well as those of the nuclei.As these membranes are made up of phospholipids, which are molecules rich in fats, we will dissolve them by using a simple household detergent.

Why do we add table salt as part of the solution of the DNA Blood extraction procedure?

Little of table salt helps to eliminate the proteins, called histones, on which the DNA is wrapped.

Why do we filter the blood solution in this experiment

? (The blood solution composed of: salt+ detergent+ water+ blood)The filtration process is used to collect the liquid rich in DNA and to separate it from the cellular remnants or any other tissues, which will be discarded.http://www.youtube.com/watch?v

=a_RTIpYUgxY

Thank you