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In the following diagram about chromosome inversion, I don't understand:

  1. Why do we need to take the reverse complement from step 1 to 2? Isn't inversion just reversing the bases in the region?
  2. How is the bottom diagram derived? For example, where does the ACCCCACTC come from? I thought it should be: GACTGCCGT for 5'→3' and CTGACGGCA for 3'→5' (inversion of the sequences in the second step).

enter image description here

http://web2.mendelu.cz/af_291_projekty2/vseo/print.php?page=315&typ=html

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Your misunderstanding probably stems from the differences of definition of inverse in bioinformatics (reverse) and cell biology/genetics.

What is shown in the picture is chromosomal inversion, in which the segment of DNA gets cut, flipped and ligated. Note that in the DNA, 5' would be ligated to 3' and vice-versa. So the 5' of the bottom strand i.e. T is ligated to the 3' of the top strand i.e. C. Similarly for the other ends. Therefore, you see a reverse complementation.

The sequence of the top strand however should have been 5'-TTAC-TGCCGTCAG-TAG-3' which has been incorrectly shown as 5'-TTAC-TGGGGTGAG-TAG-3'. That is a mistake in the picture.

Have a look at this picture [1]:

enter image description here

[1] Okamura, Kohji, John Wei, and Stephen W. Scherer. "Evolutionary implications of inversions that have caused intra-strand parity in DNA." BMC Genomics 8.1 (2007): 160.

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  • $\begingroup$ That’s what I thought as well at first but if you actually look at the sequence of the red (flipped) bit, you’ll notice that it differs between the middle and the bottom picture: the red bit reads 5′→3′ TGCCGTCAG in the middle picture, but TGGGGTGAG in the bottom picture. $\endgroup$
    – Konrad Rudolph
    Mar 23, 2016 at 14:54
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    $\begingroup$ @KonradRudolph Oh! That seems like a mistake in the picture. $\endgroup$
    – WYSIWYG
    Mar 23, 2016 at 14:57

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