def toSequence(chunk, fasta):
"""convert a list of gff attributes to a single sequence.
This function ensures correct in-order concatenation on
positive/negative strand. Overlapping regions are merged.
"""
if len(chunk) == 0: return ""
contig, strand = chunk[0].contig, chunk[0].strand
for gff in chunk:
assert gff.strand == strand, "features on different strands."
assert gff.contig == contig, "features on different contigs."
intervals = Intervals.combine([(x.start, x.end) for x in chunk])
lcontig = fasta.getLength(contig)
positive = Genomics.IsPositiveStrand(strand)
if not positive:
intervals = [(lcontig - end, lcontig - start)
for start, end in intervals]
intervals.reverse()
s = [
fasta.getSequence(contig, strand, start, end)
for start, end in intervals
]
return "".join(s)
def updateVariants(variants, lcontig, strand, phased=True):
'''update variants such that they use same coordinate
system (and strand) as the transcript
fixes 1-ness of variants
'''
new_variants = []
is_positive = Genomics.IsPositiveStrand(strand)
for variant in variants:
pos = variant.pos
genotype = bytes(variant.genotype)
reference = bytes(variant.reference)
# fix 1-ness of variants
# pos -= 1
if len(genotype) == 1:
variantseqs = list(Genomics.decodeGenotype(genotype))
has_wildtype = reference in variantseqs
action = "="
start, end = pos, pos + 1
else:
variantseqs = [x[1:] for x in genotype.split("/")]
lvariant = max([len(x) for x in variantseqs])
if not phased: variantseqs = [x for x in variantseqs if x]
has_wildtype = "*" in genotype
if "+" in genotype and "-" in genotype:
# both insertion and deletion at position
# the range is given by the deletion
# see below for explanations
if genotype.startswith("+"):
action = ">"
variantseqs[1] += "-" * (lvariant - len(variantseqs[1]))
else:
action = "<"
variantseqs[0] += "-" * (lvariant - len(variantseqs[0]))
start, end = pos + 1, pos + lvariant + 1
elif "-" in genotype:
action = "-"
# samtools: deletions are after the base denoted by snp.position
# * <- deletion at 1
# 0 1 2 3 4 5 6
# - -
# 6 5 4 3 2 1 0
# deletion of 2+3 = (2,4)
# on reverse: (7-4, 7-2) = (3,5)
start, end = pos + 1, pos + lvariant + 1
# deletions of unequal length are filled up with "-"
# This is necessary to deal with negative strands:
# -at/-atg on the positive strand deletes a t [g]
# -at/-atg on the negative strand deletes [g] t a
variantseqs = [
x + "-" * (lvariant - len(x)) for x in variantseqs
]
elif "+" in genotype:
action = "+"
# indels are after the base denoted by position
# as region use both flanking base so that negative strand
# coordinates work
# insertion between position 2 and 3
# * <- insection at pos 2
# 0 1 2i3 4
# 4 3 2i1 0
# is insertion between 1 and 2 in reverse
# including both flanking residues makes it work:
# (2,3) = (5-3,5-2) = (2,3)
# but:
# (2,4) = (5-4,5-2) = (1,3)
start, end = pos, pos + 2
# revert strand
if not is_positive:
reference = Genomics.complement(reference)
variantseqs = [Genomics.complement(x.upper()) for x in variantseqs]
start, end = lcontig - end, lcontig - start
new_variants.append(
ExtendedVariant._make((start, end, reference.upper(), action,
has_wildtype, variantseqs)))
return new_variants
