Question: Rna-Seq alignment with genome
0
gravatar for maxime.policarpo
9 months ago by
maxime.policarpo0 wrote:

Hi everybody,

I am a student in Master and i don't understand a result of rna-seq :

We have performed four alignments : Rna-seq from "PGF" cell on the genome of this cell + genome of "COX" cell Rna-seq from COX" cell on the genome of this cell + genome of "PGF" cell

Actually we have not used the whole genome map but only the short arm of Chr6 on which there is the CMH. As expected we get more reads aligned with the genome corresponding to the cell on which the rna-seq is performed but i don't understand why is the percentage of mismatch higher for rna-seq of PGF on PGF genome than for rna-seq of PGF on COX genome (The same thing happen for COX rna-seq result -> Higher mismatch when aligned with COX genome than with PGF genome).

How is that possible ? Does that mean that when we align with the good genome, we have more RNA actually corresponding to mRNA (spliced mRNA) and when we don't align with the good genome, we have more RNA corresponding to non-coding RNA ?

Thank you

rna-seq alignment • 320 views
ADD COMMENTlink modified 9 months ago • written 9 months ago by maxime.policarpo0
1

Most aligners will try to do their best to map reads. If you use an artificial small genome and if the reads are from the full genome, they may be (mis)aligned to the small genome, even though they may not have originated there.

ADD REPLYlink modified 9 months ago • written 9 months ago by genomax33k

But why would a rna-seq performed on the X genome would have more mismtach when aligned with it than a rna-seq performed on Y and aligned on X genome ? (Even if rna-seq from X have more reads aligned than the rna-seq Y)

ADD REPLYlink written 9 months ago by maxime.policarpo0

Can you clarify what X & Y genome stand for? Is the reference genome identical for this comparison?

In general terms, the two cell types (if X & Y represent that) may be expressing different genes and/or at different levels.

ADD REPLYlink modified 9 months ago • written 9 months ago by genomax33k

X genome is the PGF genome and Y genome is the COX genome. Alignment of PGF rna-seq on PGF genome give us 90% mismatch reads and alignment of COX rna-seq on PGF genome give us 60% mismatch reads !

ADD REPLYlink written 9 months ago by maxime.policarpo0
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