User:Sandbox~enwiki/Inverted Repeats

Inverted Repeats

The human genome has many nucleotide sequences that occur repeatedly and as such, can be grouped in two simple classes known as repetitive and unique sequences. These repeated DNA sequences often range from a single nucleotide to a whole gene, while the arrangement of the repeat sequences varies between widely dispersed and simple tandem arrays. The short tandem repeat sequences are observed in a few to thousands of copies dispersed all over the genome of almost all eukaryotes. The commonest repeats include the dinucleotide repeats, which have the bases AC on one DNA strand, and GT on the complementary strand. Specifically, longer repeat sequences with about 10 -100 base pairs are known as minisatellites, while shorter repeat sequences having mostly 2-4 base pairs are known as microsatellites. Some elements of the genome with unique sequences function as exons, introns and regulatory DNA. Though the most familiar loci of the repetitive sequences are the centromere, and the telomere, a large part of the repeated sequences are found among the noncoding DNA. Eukaryotes:

Eukaryotes have been observed to have most repeats compared to prokaryotes and archeabacteria. Nucleotide structure and repeats

Largely, nucleotide repeat fragments are quite often observed as part of rare DNA combinations. The three main repeats that are generally observed in particular DNA structures, include the near perfect homopurine-homopyrimidine inverted repeats or H palindromes seen in triple helical H conformations that may comprise the TAT or CGC nucleotide triads, the long inverted repeats with a tendency to form hairpins and cruciform, and the direct tandem repeats, which are common in slipped-loop structures, cruciform structures and left-handed Z-DNA.