Check if Ref matches the actual sequence, if so then return altered sequence after replacing Ref with Alt. The sequence can have multiple fragments, only check the fragment which pos >= fragment_start & pos <= fragment_end
getAltSequence(seqTable, transcriptsTable, transcriptId, pos, ref, alt)sequences table containing columns: ensembl_transcript_id and seq. seq is the sequence of a seqType region: e.g. 5' UTR sequence or 3' UTR sequence. The seqTable is output from function getSeqTable.
ensembl transcript id
nucleotides in Ref column
nucleotides in Alt column
transcripts structure table, must have 4 columns: ensembl_transcript_id, start, end, strand. start: start coordinate column in transcriptsTable for target region, for example "utr5_start", "utr3_start", or "genomic_coding_start" end: end coordinate columns in transcriptsTable for target region, for example "utr5_end", "utr3_end", or "genomic_coding_end" strand is the strand of the transcript.
Altered sequence which combines all its fragments. If Ref doesn't match the actual sequence, raise error