Classification of repeats in DNA sequences:
1) Direct (type D) AGCTTT...AGCTTT
2) Symmetric (type S) AGCTTT...TTTCGA
3) Inverted (symmetric complementary) (type I) AGCTTT...AAAGCT
4) Direct Complementary (type C) AGCTTT...TCGAAA
Presentation on double strand:
Significance of type D and I repeats is beyond any doubts; the possibility of existence of nonrandom type C repeats and a presumable effect of type S repeats on formation of the RNA structure were discussed.