Wednesday, February 23, 2011

How Is Dna Testing Done

DNA testing is done for many different reasons. DNA evidence can link an alleged criminal to the crime scene. DNA paternity and maternity testing can identify the child's father or mother. DNA relationship testing can determine if two individuals are siblings, total or partial. DNA testing can establish the ancestry of ethnic and genealogical roots.

How do the DNA test depends on the desired results and available samples. DNA fingerprint (or profile, as it also known) is the process of analysis and comparison of two DNA samples. Only identical twins have the exact DNA sequence itself, all other DNA is unique. This causes the DNA in the best way to bind people together or to places where they have been.

The entire DNA chain is very long, just in time to examine all the same. Human DNA consists of about 3. 3 billion base pairs. The differences between samples of DNA occur only in small segments of DNA - the rest of DNA is very similar. DNA testing focuses on those segments that are known to differ from person to person.

As DNA testing has evolved over time, testing methods have become more accurate and able to work with DNA samples from much smaller. The first DNA analysis was performed using drops dime size of the blood. Today's tests can extract DNA from the back of a licked stamp. The DNA must be extracted from any sample is given. DNA must be isolated and purified before it can be compared. In essence, it must be "open" the cell in which it exists. Cell walls are usually dissolved with a detergent. The proteins in the cell are digested by enzymes. After this process, DNA is purified, concentrated, and tested.

DNA testing is more often now using a process called "short tandem repeats, or STR. Human DNA has several regions of repeated sequences. These regions are in the same place in the DNA chain, but the repeated sequences are different for each individual. The "short" tandem repeats (repeated sequences of two to five base pairs in length) have been shown to provide excellent results of DNA profiles. STR is high accuracy - the possibility of misidentification of one of several billion.

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