def adjust_seq_length(self, mut_seq, orientation, full_sequence, bounds):
"""Truncate or Extend reads to make them fit the read length
When insertions or deletions are introduced to the reads, their length
will change. This function takes a (mutable) read and a reference
sequence, and extend or truncate the read if it has had an insertion
or a deletion
Args:
mut_seq (MutableSeq): a mutable sequence
orientation (string): orientation of the read. Can be 'forward' or
'reverse'
full_sequence (Seq): the reference sequence from which mut_seq
comes from
bounds (tuple): the position of the read in the full_sequence
Returns:
Seq: a sequence fitting the ErrorModel
"""
read_start, read_end = bounds
if len(mut_seq) == self.read_length:
return mut_seq.toseq()
elif len(mut_seq) > self.read_length:
while len(mut_seq) > self.read_length:
mut_seq.pop()
return mut_seq.toseq()
else: # len smaller
to_add = self.read_length - len(mut_seq)
if orientation == 'forward':
for i in range(to_add):
if read_end + i >= len(full_sequence):
nucl_to_add = 'A'
else:
nucl_to_add = str(full_sequence[read_end + i])
mut_seq.append(nucl_to_add)
elif orientation == 'reverse':
for i in range(to_add):
if read_end + i >= len(full_sequence):
nucl_to_add = 'A'
else:
nucl_to_add = util.rev_comp(full_sequence[read_end +
i])
mut_seq.append(nucl_to_add)
return mut_seq.toseq()
def test_rev_comp():
lowercase_seq = 'attgctat'
uppercase_seq = 'CCGATTAC'
assert util.rev_comp(lowercase_seq) == 'atagcaat'
assert util.rev_comp(uppercase_seq) == 'GTAATCGG'
def simulate_read(record, ErrorModel, i, cpu_number):
"""From a read pair from one genome (or sequence) according to an
ErrorModel
Each read is a SeqRecord object
returns a tuple containing the forward and reverse read.
Args:
record (SeqRecord): sequence or genome of reference
ErrorModel (ErrorModel): an ErrorModel class
i (int): a number identifying the read
cpu_number (int): cpu number. Is added to the read id.
Returns:
tuple: tuple containg a forward read and a reverse read
"""
logger = logging.getLogger(__name__)
sequence = record.seq
header = record.id
read_length = ErrorModel.read_length
insert_size = ErrorModel.random_insert_size()
# generate the forward read
try: # a ref sequence has to be longer than 2 * read_length + i_size
assert read_length < len(record.seq)
forward_start = random.randrange(
0,
len(record.seq) - (2 * read_length + insert_size))
except AssertionError as e:
logger.error('%s shorter than read length for this ErrorModel:%s' %
(e, record.id))
sys.exit(1)
except ValueError as e:
logger.debug('%s shorter than template length for this ErrorModel:%s' %
(record.id, e))
forward_start = max(0,
random.randrange(0,
len(record.seq) - read_length))
# raise
forward_end = forward_start + read_length
bounds = (forward_start, forward_end)
# create a perfect read
forward = SeqRecord(Seq(str(sequence[forward_start:forward_end]),
IUPAC.unambiguous_dna),
id='%s_%s_%s/1' % (header, i, cpu_number),
description='')
# add the indels, the qual scores and modify the record accordingly
forward.seq = ErrorModel.introduce_indels(forward, 'forward', sequence,
bounds)
forward = ErrorModel.introduce_error_scores(forward, 'forward')
forward.seq = ErrorModel.mut_sequence(forward, 'forward')
# generate the reverse read
try:
reverse_start = forward_end + insert_size
reverse_end = reverse_start + read_length
assert reverse_end < len(record.seq)
except AssertionError as e:
# we use random insert when the modelled template length distribution
# is too large
reverse_end = random.randrange(read_length, len(record.seq))
reverse_start = reverse_end - read_length
bounds = (reverse_start, reverse_end)
# create a perfect read
reverse = SeqRecord(Seq(rev_comp(str(sequence[reverse_start:reverse_end])),
IUPAC.unambiguous_dna),
id='%s_%s_%s/2' % (header, i, cpu_number),
description='')
# add the indels, the qual scores and modify the record accordingly
reverse.seq = ErrorModel.introduce_indels(reverse, 'reverse', sequence,
bounds)
reverse = ErrorModel.introduce_error_scores(reverse, 'reverse')
reverse.seq = ErrorModel.mut_sequence(reverse, 'reverse')
return (forward, reverse)
def simulate_read_with_error_model(cls,
genome,
ErrorModel,
i,
always_forward=True):
"""Form a read from one genome (or sequence) according to an
ErrorModel
returns a string
Args:
genome (string): sequence or genome of reference
ErrorModel (ErrorModel): an ErrorModel class
i (int): a number identifying the read
Returns:
string: a string representing a single read
"""
# ErrorModel.read_length = ErrorModel.read_length - 1
np_random = np.random.RandomState(seed=i)
read_length = ErrorModel.read_length
if len(genome) <= read_length:
genome = "".join([genome, "N" * (read_length - len(genome) + 1)])
record = SeqRecord(Seq(genome, IUPAC.unambiguous_dna),
id=f'genome_{i}',
description='')
sequence = record.seq
header = record.id
# generate the forward read
forward_start = np_random.randint(
low=0, high=max(len(record.seq) - read_length + 1, 1))
forward_end = forward_start + read_length
generate_forward = np_random.randint(low=0, high=2)
if generate_forward or always_forward:
bounds = (forward_start, forward_end)
# create a perfect read
forward = SeqRecord(Seq(str(sequence[forward_start:forward_end]),
IUPAC.unambiguous_dna),
id='%s_%s' % (header, i),
description='')
# add the indels, the qual scores and modify the record accordingly
forward.seq = ErrorModel.introduce_indels(forward, 'forward',
sequence, bounds)
forward = ErrorModel.introduce_error_scores(forward, 'forward')
forward.seq = ErrorModel.mut_sequence(forward, 'forward')
return str(forward.seq)
else:
insert_size = ErrorModel.random_insert_size()
try:
reverse_start = forward_end + insert_size
reverse_end = reverse_start + read_length
assert reverse_end < len(record.seq)
except AssertionError:
reverse_end = np_random.randint(low=read_length,
high=len(record.seq))
reverse_start = reverse_end - read_length
bounds = (reverse_start, reverse_end)
reverse = SeqRecord(Seq(
rev_comp(str(sequence[reverse_start:reverse_end])),
IUPAC.unambiguous_dna),
id='%s_%s' % (header, i),
description='')
reverse.seq = ErrorModel.introduce_indels(reverse, 'reverse',
sequence, bounds)
reverse = ErrorModel.introduce_error_scores(reverse, 'reverse')
reverse.seq = ErrorModel.mut_sequence(reverse, 'reverse')
return str(reverse.seq)
