Genetic Testing Dna Test Rflp Analysis

RFLP analysis is one of the older methods of DNA testing. First developed in the 1970s, it still has many uses. The actual analysis time is lengthy and complicated, but is also less prone to error. RFLP analysis and PCR analysis are the two most common techniques used in a variety of scientific areas, including genetics and forensics.

RFLP Overview

RFLP stands for “restriction fragment length polymorphism.” The first two words refer to the process of DNA fragmenting with specially applied enzymes. Once this takes place, the DNA strands break up into various lengths. Polymorphism in Greek means “many shapes.” This word references the multiple shapes, or lengths, that can result in a definitive match distinctive to each human being. A biochemist from Scotland, Edward Southern, developed this procedure, also known as “Southern blotting.”

The term “RFLP” is sometimes called “rif-lip.” Although used much less, it remains beneficial in mapping human DNA when larger samples are easier to collect. Newer variants of RFLP also exist in DNA testing.

Uses for RFLP Analysis

In DNA analysis RFLP has many uses, including:

  • crime
  • forensics
  • disease
  • genetics
  • paternity.

In fact, RFLP is especially helpful in determining who is at risk for inheriting certain diseases. A testing of the general population, including those who have specific genetic disease markers, produces valid samples for comparison. Several drawbacks exist, however. Dependable RFLP analysis requires larger tissue samples, which is not possible in many cases. The technique is also ineffective if tissue samples are older or contaminated. Degraded DNA RFLP analysis is also of little use.

How RFLP Analysis Works

RFLP analysis looks at how the segments in a sampling of DNA line up. Larger fragments pair in one group, while like-sized smaller pieces also cling together. It is these samplings, when compared against others, which show unique banding patterns. For instance, in the case of an RFLP analysis of semen, collected samples from the victim and the accused perpetrator can result in a match. If crime scene evidence is the only sampling available, RFLP analysis is beneficial in comparisons against national DNA databases of known criminals.

In the case of paternity testing, the child ‘s DNA will reflect a sequencing that matches with both parents. It is extremely unlikely that two unrelated individuals will show the same banding patterns on an RFLP test. For many legal issues, this evidence is often enough to be conclusive. In family genetic testing, DNA from all related parties may provide answers to hereditary diseases.

In the search for disease markers, sometimes a missing segment becomes the key. The breast cancer gene, BRCA1, is one such example. Under extensive RFLP comparisons, a marker was present only in women who had a family history of the disease. It was not present in women who had breast cancer, but no history. From this success, other RFLP banding tests are proving to provide insight into other serious conditions including prostate cancer and cystic fibrosis. Many researchers believe that, in time, this type of sequencing will help detect hundreds of hereditary diseases.

The RFLP Technique

While the actual process is quite complex, this is a simple explanation of the steps in analysis.

Every cell contains a complete sample of DNA. RFLP analysis requires thousands of complete DNA samples for accuracy. A “restriction enzyme,” applied to each complete DNA molecule will create fragments of various lengths by dissolving the DNA. Several types of enzymes exist for testing, each with specific types of targeting. For every individual, the multiple DNA molecules fragment in exactly the same way. Next, a process called “gel electrophoresis” creates the pairing of same-sized fragments. This is essentially an electrical process that works similar to magnetizing. As the pieces slide through the special “gel ” device, they tend to separate based on their sizes. A “blot” replicates the exact position of each fragment.

A DNA “probe” identifies the DNA markers, those that will determine its unique banding characteristics. This probe is simply a small DNA segment that attaches to matching sequences, leaving an easy to recognize pattern. An X-ray of the blot provides a picture of the sequencing.

This lengthy process can take weeks in carefully controlled environments with skilled technicians. Newer processes continue to improve on accuracy and speed.

Resources

Bio.davidson.edu (2001). RFLP Method — Restriction Fragment Length Polymorphism. Retrieved September 5, 2008, from the Davidson College Web site: http://www.bio.davidson.edu/COURSES/genomics/method/RFLP.html.

Biology.buffalo.edu (n.d.) Applications of Genomic Analysis. Retrieved September 5, 2008, from the Department of Biological Sciences at the University at Buffalo Web site: http://www.biology.buffalo.edu/courses/bio531/lecture14.html.

Riley, Donald E. Ph.D. (2006). DNA Testing: An Introduction For Non-Scientists. An Illustrated Explanation. Retrieved September 5, 2008, from Scientific Testimony Web site: http://www.scientific.org/tutorials/articles/riley/riley.html.