After reading -

(wikipedia) Tandem repeats occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other.

( a paper) A tandem repeat in DNA is two or more contiguous, approximate copies of a pattern of nucleotides.

I deduced that the portion of oriC containing all four 9mer-s was to be called a tandem repeat and it together with all three 13 mer-s, two tandem repeats.

But again while reading Principles of genetics by Simmons I stumbled upon the following-

The single ori in E.coli has been characterised in considerable detail. It is 245 nucleotide pair long and contains two repeated sequences. One 13-bp is present in three tandem repeats. The three repeats are rich in ...

So here it says that each 9-mer in the series is a tandem repeat actually.

Which meaning is more accepted?

  • $\begingroup$ I don't know much about Simmons, but the definition by wikipedia is seemingly more accepted. $\endgroup$ – another 'Homo sapien' Dec 3 '16 at 15:44

The DNA sequence "TATATATA" contains 4 repeats of the 2-mer "TA" and because these repeats are adjacent to each other, they are tandem repeats. The pattern of nucleotides is repeated and the repetitions are next to each other.

This is what both the Wikipedia and the Simmons definitions are trying to communicate. The statement you quote from Benson'a paper can be taken to mean the same thing (except for "approximate"), but might also be construed as saying the collection of all contiguous repeats is one tandem repeat, but that is not what was intended.

So, the oriC sequence has 4 tandem repeats of one kind (9-mers) and 3 tandem repeats of another pattern (13-mers).


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