To a large extent, portions of nucleotide repeats are quite often observed as part of rare DNA combinations. The three main repeats which are largely found in particular DNA constructs include the closely precise homopurine-homopyrimidine inverted repeats, which is otherwise referred to as H palindromes, a common occurrence in triple helical H conformations that may comprise either the TAT or CGC nucleotide triads. The others could be described as long inverted repeats having the tendency to produce hairpins and cruciform, and finally direct tandem repeats, which commonly exist in structures described as slipped-loop, cruciform and left-handed Z-DNA.