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Janet Young
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@janet-young-2360
Last seen 5.1 years ago
Fred Hutchinson Cancer Research Center,…
Hi there, (I think it'll probably be Valerie looking at this question
- hi Valerie),
I'm just beginning to look at using VariantAnnotation to annotate some
SNPs I've called on some yeast data (sacCer3). I can see this will be
a really useful package for me - thanks!
I can see that chrM (mitochiondrial) SNPs are currently not included
in the output of predictCoding, and then using locateVariants, all of
chrM SNPs get annotated as intergenic/NA (with a warning, that we
ignore circular chromosomes). I can understand why that is - circular
chromosomes, and a different genetic code make it trickier. Fair
enough.
I'm wondering what the prospects are regarding chrM SNPs in the future
- any plans to include those later?
I'm also wondering whether I can use some hacks to get chrM SNPs
annotated. Two questions/potential issues related to that I wanted to
ask you guys about:
1. are alternative codon tables already supported anywhere in
Bioconductor? Using "?GENETIC_CODE" it looks like this is defined
in Biostrings, and it looks like only the standard nuclear code is
defined. Are the various alternative genetic codes defined anywhere?
For this project, I'm interested in the yeast mitochondrial code, and
for another I'm interested in the fly mitochondrial code. It'd be
great if we could have all the codes available (I've got another
project looking at ciliate nuclear sequences, for example - not
working with translations yet, but maybe later...)
With a little work, I'll be able to save flat files from NCBI
(http://www.ncbi.nlm.nih.gov/Taxonomy/Utils/wprintgc.cgi), and read
those in and transform them to a character vector that looks like
GENETIC_CODE. But I realise it might be something useful to have
encoded more centrally, so thought I'd ask.
2. What issues should I think about for the circular chromosomes?
I'm thinking of a slightly hacky solution where I ignore any
annotated ORFs that wrap around from the end of the chromosome to the
beginning, and then just treating it as a linear chromosome.
Actually, in my case (using sacCer3) there are no ORFs spanning the
break in the circular chromosome, so I don't think I'll miss any
annotations. Turns out the same is true for human (hg19 knownGene
annotations), so maybe the circular chromosome issue isn't such a big
issue after all?
It seems like that should work, but any thoughts from you - you've
thought about these questions a lot more than I have?
Looking forward to hearing any thoughts you have. I know sometimes
people just ignore the chrM SNPs, but it'd be nice to take a slightly
more comprehensive approach if possible.
thanks in advance for any input you have,
Janet
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Dr. Janet Young
Malik lab
http://research.fhcrc.org/malik/en.html
Fred Hutchinson Cancer Research Center
1100 Fairview Avenue N., A2-025,
P.O. Box 19024, Seattle, WA 98109-1024, USA.
tel: (206) 667 4512
email: jayoung ...at... fhcrc.org
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