Hi,

I would like to download the FASTA files of all genes without an intron. 


In R you could do something like this to get all transcript with only one exon (thus intronless)

    library(biomaRt)
    library(dplyr)
    
    ensembl = useEnsembl(biomart="ensembl", dataset="hsapiens_gene_ensembl")
    # will give you one line per exon
    gene <- getBM(attributes=c('ensembl_gene_id','ensembl_transcript_id','hgnc_symbol','ensembl_exon_id'), mart = ensembl)
    
    # extract all transcript with only one exon
    gene.oneExon <- 
      gene %>% 
      group_by(ensembl_transcript_id) %>%
      summarise(n=n()) %>%
      filter(n==1)
    
    # get sequence of associated transcript
    gene.oneExon.seq <- getSequence(id=gene.oneExon$ensembl_transcript_id,type="ensembl_transcript_id", seqType="gene_exon",mart=ensembl)

