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Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
All tandem repeat arrays are classifiable as satellite DNA, a name originating from the fact that tandem DNA repeats, by nature of repeating the same nucleotide sequences repeatedly, have a unique ratio of the two possible nucleotide base pair combinations, conferring them a specific mass density that allows them to be separated from the rest of the genome with density-based laboratory ...
The system of DNA profiling used today is based on PCR and uses simple sequences [6] or short tandem repeats (STR). This method uses highly polymorphic regions that have short repeated sequences of DNA (the most common is 4 bases repeated, but there are other lengths in use, including 3 and 5 bases).
A microsatellite is a tract of tandemly repeated (i.e. adjacent) DNA motifs that range in length from one to six or up to ten nucleotides (the exact definition and delineation to the longer minisatellites varies from author to author), [1] [6] and are typically repeated 5–50 times.
Since a sequence of single-stranded DNA needs to find its complementary strand to reform a double helix, common sequences renature more rapidly than rare sequences. Indeed, the rate at which a sequence will reassociate is proportional to the number of copies of that sequence in the DNA sample. A sample with a highly-repetitive sequence will ...
If coding sequences are degraded in this process, potentially vital genetic code would be lost. Telomeres are non-coding, repetitive sequences located at the termini of linear chromosomes to act as buffers for those coding sequences further behind. They "cap" the end-sequences and are progressively degraded in the process of DNA replication.
Minisatellites are a type of DNA tandem repeat sequence, meaning that the sequences repeat one after another without other sequences or nucleotides in between them. Minisatellites are characterized by a repeat sequence of about ten to one hundred nucleotides, and the number of times the sequence repeats varies from about five to fifty times.
For example, minisatellite DNA is a short region (1-5 kb) of repeating elements with length >9 nucleotides. Whereas microsatellites in DNA sequences are considered to have a length of 1-8 nucleotides. [8] The difference in how many of the repeats is present in the region (length of the region) is the basis for DNA profiling. [citation needed]