Minisatellites are small portions of DNA responsible for human genetic traits. They are highly variable and have high mutation rates, making them useful for research purposes such as DNA fingerprinting and studying cancer. Minisatellite DNA is inherently unstable and does not code for any expressed genetic trait, but may play a role in protecting chromosomes from damage and contributing to the aging process.
A minisatellite is a small portion of the deoxyribonucleic acid (DNA) macromolecule responsible for coding and transferring human genetic characteristics. This molecule consists of a ladder structure of alternating base pairs of phosphate and deoxyribose molecules. In the case of a minisatellite, there are often only 10 to 60 base pairs, but sometimes there may be 100 or more. These minisatellites are known to exist in more than 1,000 locations in the human genome, which codes for all of an organism’s genetic traits.
The first minisatellite molecule was discovered by AR Wyman and R. White at the National Institutes of Health (NIH) in the United States in 1980. This led to their use for the practice of DNA fingerprinting in forensic crime. They were later found to be hypervariable or hypermutable, with an average base mutation rate of up to 20%. This classified the minisatellite as the most unstable region of the human genome.
There are also microsatellite portions of DNA, in which the genetic sequences consist of only two to five base pairs. Due to the fact that both minisatellite and microsatellite structures are highly variable and have high mutation rates, they are used frequently in a variety of researches. The purposes for which they are used include forensically identifying an individual’s genetic parents, mapping genetic variation in the human population, and studying cancer. Long minisatellite arrays that exceed 100 base pairs in length are considered very unstable. Research on mice has shown that they have a mutation rate of up to 100%, especially in the cerebellum part of the brain.
The reason minisatellite DNA is considered inherently unstable is that it is a repeating sequence of base pairs of DNA that does not appear to code for any expressed genetic trait. These minisatellite molecules are present in a wide variety of animals and other organisms, such as bacteria. Like introns, which are also non-coding segments of DNA, minisatellite DNA performs no understood function. However, they have been associated with disorders such as Huntington’s disease and various types of cancer.
One possible purpose for minisatellite DNA could be the role they play where they exist at the tip of telomeres. A telomere is a segment of DNA at the end of a chromosome that serves to protect the chromosome from damage and loss of genetic coding sequences used in the cell division process. Shortening of telomeres is known to contribute to the aging process, and laboratory experiments to extend telomere length have kept cells healthy beyond their normal lifespan. In fact, the telomerase enzyme that maintains telomeres is also activated by cancer cells, giving them a level of virtual immortality.
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