Inward oriented pairs and outward oriented pairs from a BAM file - Bamcheck vs Samtools
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7.7 years ago
Prakki Rama ★ 2.7k

Hi all,

I was trying to find the inward oriented pairs (innies) and outward oriented pairs (outties) using Bamcheck and Samtools. Both gave me different results on running. May I know which one to pick from both? Any suggestions or comments are welcome! enter image description here

sam bam pairs reads • 5.4k views
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My guess would be that these are handling dovetailed and or bookended reads differently. Since the files are small, just subset them until you find a single alignment that causes the numbers to differ and then have a look at that.

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Thanks Devon Ryan. I will try to look at that. May I know what it means by dovetailed and bookended reads?

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That nomenclature is borrowed from bowtie2, though I probably meant "contain" rather than "bookend".

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7.7 years ago
Prakki Rama ★ 2.7k

I will answer this question myself. I was continuously trying to test this, on a small .bam file as @Devon has suggested.

Finally,

samtools stats seems to be giving me correct results.

I have done this by converting bam file to bed file, and then took the reads coordinates, along with orientations and counted the number of inward and outward pairs. As a side point, It appears that that samtools will also take care of an extra step that if it finds two reads in a pair (either innie or outtie) to be overlapping, it ignores them and does not report as either inward pair or outward pair, although by direction they are either facing (--> <--) or not facing other (<-- -->).

I have looked outward pairs in a third party visualization tool called tablet, which showed them as outward and improperly paired.

Screenshot.

On the other hand,

bamcheck failed to recognize any outward pairs from my bam file (which can be noticed from the screenshot in the question).

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I have added more details in my blog post.

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One fewer mystery in life :)

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@Devon: Yes. Atleast for me. :)

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@Prakki Rama: The link for the screenshot image you had included is not working at the time I am writing this.

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@genomax2; It should be available now. Thanks.

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