Introns in exons and vice versa (Genomic Features)
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@fenton-christopher-graham-5504
Last seen 4.9 years ago
library(GenomicFeatures) #get known genes genes <- makeTranscriptDbFromUCSC(genome = "hg19",tablename = "knownGene") saveFeatures(genes, file="hg19_knownGene.sqlite") txdb <- loadFeatures("hg19_knownGene.sqlite") #get introns introns <- intronsByTranscript(txdb) introns <- unlist(introns) #get exons exons <- exonsBy(txdb) exons <- unlist(exons) #take chr1 and "+" stand introns_ind <- which(seqnames(introns) == "chr1" & strand(introns) == "+") exons_ind <- which(seqnames(exons) == "chr1" & stand(exons) == "+") #convert to ranges introns_chr1 <- ranges(introns[introns_ind,]) exons_chr1 <- ranges(exons[exons_ind,]) #look for introns in exons? sum(countOverlaps(introns_chr1, exons_chr1, type="within")) Why isn't this number 0? Why are we looking at over 1000 introns within exons? Chris
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@sean-davis-490
Last seen 12 weeks ago
United States
On Wed, Oct 3, 2012 at 6:50 AM, Fenton Christopher Graham <christopher.fenton at="" uit.no=""> wrote: > library(GenomicFeatures) > > #get known genes > genes <- makeTranscriptDbFromUCSC(genome = "hg19",tablename = "knownGene") > saveFeatures(genes, file="hg19_knownGene.sqlite") > txdb <- loadFeatures("hg19_knownGene.sqlite") > > #get introns > introns <- intronsByTranscript(txdb) > introns <- unlist(introns) > > #get exons > exons <- exonsBy(txdb) > exons <- unlist(exons) > > #take chr1 and "+" stand > introns_ind <- which(seqnames(introns) == "chr1" & strand(introns) == "+") > exons_ind <- which(seqnames(exons) == "chr1" & stand(exons) == "+") > > #convert to ranges > introns_chr1 <- ranges(introns[introns_ind,]) > exons_chr1 <- ranges(exons[exons_ind,]) > > #look for introns in exons? > sum(countOverlaps(introns_chr1, exons_chr1, type="within")) > > Why isn't this number 0? > Why are we looking at over 1000 introns within exons? The genome is a strange place, isn't it? To see what is going on, extend your example just a bit: intronsWithinExons_ind = queryHits(findOverlaps(introns_chr1,exons_chr1,type='within')) intronsWithinExons = introns_chr1[intronsWithinExons_ind,] Try looking at a few of these in the UCSC genome browser. The few I checked are there. Sean
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Thanks, though that each transcript (splice variant) would negate overlap. But I see from UCSC and the code, that the logic is flawed, and not the genome. Chris ________________________________________ Fra: seandavi at gmail.com [seandavi at gmail.com] på vegne av Sean Davis [sdavis2 at mail.nih.gov] Sendt: 3. oktober 2012 13:12 Til: Fenton Christopher Graham Kopi: bioconductor Emne: Re: [BioC] Introns in exons and vice versa (Genomic Features) On Wed, Oct 3, 2012 at 6:50 AM, Fenton Christopher Graham <christopher.fenton at="" uit.no=""> wrote: > library(GenomicFeatures) > > #get known genes > genes <- makeTranscriptDbFromUCSC(genome = "hg19",tablename = "knownGene") > saveFeatures(genes, file="hg19_knownGene.sqlite") > txdb <- loadFeatures("hg19_knownGene.sqlite") > > #get introns > introns <- intronsByTranscript(txdb) > introns <- unlist(introns) > > #get exons > exons <- exonsBy(txdb) > exons <- unlist(exons) > > #take chr1 and "+" stand > introns_ind <- which(seqnames(introns) == "chr1" & strand(introns) == "+") > exons_ind <- which(seqnames(exons) == "chr1" & stand(exons) == "+") > > #convert to ranges > introns_chr1 <- ranges(introns[introns_ind,]) > exons_chr1 <- ranges(exons[exons_ind,]) > > #look for introns in exons? > sum(countOverlaps(introns_chr1, exons_chr1, type="within")) > > Why isn't this number 0? > Why are we looking at over 1000 introns within exons? The genome is a strange place, isn't it? To see what is going on, extend your example just a bit: intronsWithinExons_ind = queryHits(findOverlaps(introns_chr1,exons_chr1,type='within')) intronsWithinExons = introns_chr1[intronsWithinExons_ind,] Try looking at a few of these in the UCSC genome browser. The few I checked are there. Sean
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@alex-gutteridge-2935
Last seen 10.1 years ago
United States
On 03.10.2012 11:50, Fenton Christopher Graham wrote: > library(GenomicFeatures) > > #get known genes > genes <- makeTranscriptDbFromUCSC(genome = "hg19",tablename = > "knownGene") > saveFeatures(genes, file="hg19_knownGene.sqlite") > txdb <- loadFeatures("hg19_knownGene.sqlite") > > #get introns > introns <- intronsByTranscript(txdb) > introns <- unlist(introns) > > #get exons > exons <- exonsBy(txdb) > exons <- unlist(exons) > > #take chr1 and "+" stand > introns_ind <- which(seqnames(introns) == "chr1" & strand(introns) > == "+") > exons_ind <- which(seqnames(exons) == "chr1" & stand(exons) == "+") > > #convert to ranges > introns_chr1 <- ranges(introns[introns_ind,]) > exons_chr1 <- ranges(exons[exons_ind,]) > > #look for introns in exons? > sum(countOverlaps(introns_chr1, exons_chr1, type="within")) > > Why isn't this number 0? > Why are we looking at over 1000 introns within exons? > > > Chris Alternative splicing. An exon in one transcript from a given gene may well have introns removed in other transcripts from the same gene (and will hence overlap). -- Alex Gutteridge
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