V.+DNA


 * __ DNA __ **
 * DNA is the short form for deoxyribonucleic acid it was first discovered in 1868.
 * The first actual breakthrough in how DNA actually works occurred in the early 1950s by two researchers who broke down the structure of DNA.
 * Genes are the basic units of heredity which are located on chromosomes
 * Chromosomes are rod-like structures that can be found in the nucleus of every cell in the body except for red blood cells.
 * There are usually 46 chromosomes in all human cells, with 23 pairs each.
 * DNA is a polymer which means that it is a large molecule made by linking a series of repeating units called nucleotides.
 * A nucleotide is made up of a sugar molecule, a phosphorus atom, surrounded by four oxygen atoms and a nitrogen containing molecule which is called a base.
 * There are 4 types of bases which belong to DNA, they are: adenine, guanine, thymine, cytosine.
 * DNA is composed of two strands that are coiled into a double helix.
 * Adenine and thymine are paired together on the double helix and so are guanine and cytosine which is also known as complementary base pairing. This order explains the differences between DNA strands.
 * DNA is found practically everywhere in the human body such as in blood, skin cells, bones, teeth, saliva, hair, finger nails.
 * Everyone has the same chemical structure of DNA, it is the order in which the bases are paired that is unique because there are millions of base pairs which makes everyone different.
 * Two Types of DNA **
 * There are two types of DNA which can be used for forensics testing purposes.

1. Nuclear DNA
 * Every cell has a nucleus which contains most of our DNA
 * This DNA is usually a mixture of the mother and father’s DNA.
 * Nuclear DNA is primarily analyzed during forensic identity testing.
 * Our physical appearance and make up consists of nuclear DNA.

2. Mitochondrial DNA (mtDNA)
 * This DNA is inherited only from the mother so this means that when trying to identify a person it can be linked to the same maternal lineage.
 * Found outside of the nucleus of the cell.
 * Mitochondria are structures within cells that provide energy to cells in order to function
 * In every cell there can be hundreds of mitochondria to be found.
 * It is easier to find mitochondrial DNA in comparison to nuclear DNA due to the fact that our bodies contain about 500 to 1000 copies of the mitochondrial DNA.
 * Mitochondrial DNA is usually used when a sufficient amount of nuclear DNA is not available.
 * The analyzing of mtDNA requires much more time, work, and money and is not used very often



**__ Forensics: __**

DNA is useful in many ways. It can connect individuals to locations, objects, or other people. It can also be the most damning evidence in murder and sexual assault cases. DNA is a recent tool in the forensic teams arsenal, and therefore could not be applied in the Clifford Olson case. However, DNA samples can be conserved, and future testing can be done. There are two forms of testing:

The earliest form of DNA testing used by forensic scientists was called ** RFLP Typing. ** RFLP uses a Variable Number of Tandem Repeats or VNTR, which are portions of the DNA molecule that contain sequences of bases that are repeated numerous times. These repeating sequences are called tandem repeats. These tandem repeats offer a means of distinguishing individuals from one another. The exact number of repeated sequences varies from person to person, along with the differences in the length of the DNA strands, which are called restriction fragment length polymorphisms. This form of DNA profiling has now been re-evaluated and new forms of testing are used today for the productivity.

** Polymerase Chain Reaction ** (PCR) is the second and most efficient method used for DNA profiling today. It mimics the cell’s ability to replicate its own DNA, by heating it to separate it, and then primers (short strands of DNA used to target specific regions of DNA for replication) are added. Lastly, DNA polymerase and free nucleotides are added to rebuild each of the separated strands. This process is repeated 25 to 30 times, to create a viable sample. This process is extremely useful with small DNA samples, and is far less time consuming.

** Short Tandem Repeat (STR) DNA Typing: ** Is based on PCR DNA profiling. This is the most widely used DNA profiling procedure. STRs are locations on the chromosome that contain short sequences that repeat themselves within the DNA molecule. They are useful markers for identification because they are found in great abundance throughout the human genome. STRs consist of repeating sequences of 3 to 7 bases in length; therefore the entire strand of an STR is very short. This form of DNA profiling is less susceptible to degradation, and may be recovered from bodies or stains that have been subjected to extreme decomposition. STRs are ideal candidates for multiplication by PCR because of their short length. ** Multiplexing ** is a technique that simultaneously detects more than one DNA marker in a single analysis. There are hundreds of different types of STRs are found in human genes, and the more STRs one can characterize, the smaller the percentage of the population from which a particular combination of STRs can emanate. United States crime laboratories have standardized on 13 STRs for entry into a national database that has been named CODIS. There is a high degree of discrimination and even individualization can be attained by analyzing a combination of STRs (multiplexing) and determining the product of their frequencies. ** Capillary Electrophoresis ** separates the DNA fragments on a thin glass column. Each end of the column is immersed in a reservoir of buffer liquid with electrodes. DNA containing sample solution is injected into one end of the column. The STR fragments move through the electrified column at a speed that is related to the length of the STR fragments. As the DNA peaks pass through the detector they are recorded on a display known as an // electropherogram. //

Therefore, if DNA was available during the time of this case, it would have been very useful to prove Clifford Olson’s guilt, before he was able to kill as many children as he did.