Harvard:Biophysics 101/2007/Notebook:Michael Wang/2007-5-1

Here's the code for a function that compares a query and reference sequence, returning a list of mutation objects that specify its position in both sequences. Its based on the program wrote a long time ago. The actual useful function is called: def getAllMutations (referenceSequence, querySequence):

Here is the mutation object: class mutation: def __init__(self,type="",ref_span=[0,0],other_span=[0,0]): self.type = type self.ref_span = ref_span self.other_span = other_span

And here is the code: import re from Bio import Transcribe transcriber = Transcribe.unambiguous_transcriber from Bio import Translate from Bio.Alphabet import IUPAC from Bio.Seq import Seq import os from Bio import Clustalw standard_translator = Translate.unambiguous_dna_by_id[1]
 * 1) find all orfs within the sequences

class codon: def __init__(self, sequence=""): self.sequence = sequence self.mRNA = transcriber.transcribe(Seq(sequence, IUPAC.unambiguous_dna)) self.protein = standard_translator.translate(Seq(sequence, IUPAC.unambiguous_dna))[0]

class raw_mutation: def __init__(self,type="",ref_location=0,other_location=0): self.type = type self.ref_location=ref_location self.other_location = other_location

class mutation: def __init__(self,type="",ref_span=[0,0],other_span=[0,0]): self.type = type self.ref_span = ref_span self.other_span = other_span class orf: #On initiation, the orf is stored as a list of codons. If the orf has no stop, any excess bases will #be ignored on the conversion to codons def __init__(self, source="", source_span=[]): self.source = source self.codons = [] self.sequence = source[source_span[0]:source_span[1]] for i in range(len(self.sequence)/3): temp_codon = codon(self.sequence[i*3:3+(i*3)]) #this algorithm of seperating into codons ignores any excess bases self.codons.append(temp_codon) #orfs are indexed by codons def __getitem__(self,index): return self.codons[index]

def find_mutations(self,other): refPos = 0 seqPos = 0 #print "Ref:",self #print "Other:",other all_mutations = [] for i in range(len(self)): #print self[i], " ", other[i], ' ', refPos, ' ', seqPos if self[i] != other[i]: if self[i] == '-': new_mutation = raw_mutation("insertion",refPos,seqPos) elif other[i] == '-': new_mutation = raw_mutation("deletion",refPos,seqPos) else: new_mutation = raw_mutation("point",refPos,seqPos) all_mutations.append(new_mutation) #print "Mutation!" print new_mutation.type," ",new_mutation.ref_location," ",new_mutation.other_location if self[i] != '-': refPos += 1 if other[i] != '-': seqPos += 1 return all_mutations def consolidate_mutations(raw_mutations): #I think this will have a bug for insertions before the first base of the refseq because #in every other case, ref_loc will refer to the base before the insertion consolidated_mutations =[] i = 0 while i < len(raw_mutations): #print "outer loop" current_type = raw_mutations[i].type if(current_type == "point"): ref_loc = raw_mutations[i].ref_location other_loc = raw_mutations[i].other_location new_mutation = mutation("point",[ref_loc,ref_loc],[other_loc,other_loc]) consolidated_mutations.append(new_mutation) i += 1 elif(current_type == "deletion") or (current_type == "insertion"): ref_start = raw_mutations[i].ref_location other_start = raw_mutations[i].other_location ref_end = raw_mutations[i].ref_location other_end = raw_mutations[i].other_location i += 1 #It would have been nice to have a do while here... while (i<=len(raw_mutations)): #and (raw_mutations[i].type == current_type): #hopefully it exits after the first condition so it doesn't go past array length if (i==len(raw_mutations)) or ((raw_mutations[i].ref_location!=ref_start) and (raw_mutations[i].other_location!=other_start)): new_mutation = mutation(current_type,[ref_start,ref_end],[other_start,other_end]) consolidated_mutations.append(new_mutation) print current_type, "found at ", "ref", ref_start, ",",ref_end," seq ", other_start, ",", other_end break elif (current_type == "insertion"): #and (raw_mutations[i].ref_location==ref_start): other_end += 1 i += 1 #print "extending insertion" elif (current_type == "deletion"): #and (raw_mutations[i].ref_location==other_start): ref_end += 1 i += 1 #print "extending deletion" else: print "I shouldn't be here!!!" break

return consolidated_mutations def findORFS(sequence, startpos=0): all_orfs = [] start = re.compile('ATG') stop = re.compile('(TAA|TGA|TAG)') all_starts = start.finditer(sequence) all_stops = stop.finditer(sequence) all_starts_list = [] for match in all_starts: all_starts_list.append(match.span) all_stops_list = [] for stops in all_stops: all_stops_list.append(stops.span) #print stops.span for start in all_starts_list: found = 0 for stop in all_stops_list: diff = (stop[0]-start[0]) if ((diff>0) and ((diff%3) == 0)): print "orf at:", start[0]," ",stop[1] all_orfs.append((start[0],stop[1])) found = 1 break if found ==0: all_orfs.append((start[0],None)) return all_orfs

def getAllMutations (referenceSequence, querySequence): teststring = re.sub("\s+", "", referenceSequence) teststring2 = re.sub("\s+", "", querySequence) allspans = findORFS(teststring) allspans2 = findORFS(teststring2) allorfs = [] allorfs2 = [] print "spans" print allspans2 for i in allspans: x = i[0] #I don't know why it won't let me use i[0] and i[1] directly as an int y = i[1] temp_orf = orf(teststring,i) allorfs.append(temp_orf) print "orfs2" for i in allspans2: x = i[0] #I don't know why it won't let me use i[0] and i[1] directly as an int y = i[1] temp_orf = orf(teststring2,i) allorfs2.append(temp_orf) print temp_orf.sequence temp_file = open(os.path.join(os.curdir, 'temp.txt'),"w") temp_file.write(">gi|23509994|ref|NC_004318.1| Plasmodium\n ") temp_file.write(teststring) temp_file.write("\n\n") temp_file.write(">gi|239809994|ref|NC_004318.1| Plasmodium\n ") temp_file.write(teststring2) temp_file.close cline = Clustalw.MultipleAlignCL(os.path.join(os.curdir, 'temp.txt')) cline.set_output('test.aln') alignment = Clustalw.do_alignment(cline) all_records = alignment.get_all_seqs print alignment mutations = find_mutations(all_records[0].seq,all_records[1].seq) all_real = consolidate_mutations (mutations) return all_real

all_real = consolidate_mutations (mutations) #for i in ref_orfs:
 * 1) print mutations
 * 1) def is_silent(mutation, ref_orfs):


 * 1) def is_frameshift(mutation, all_orfs):

teststring = " A TGG GGG GGA ATG ATT AAC GTC GTT AAA GTA TGT TTT TT" teststring2= "CGA ATG GGG GCG ATG ATT AAC C GTT AAA GTA TGT TTT TTG TAG" all_real = getAllMutations(teststring,teststring2) for i in all_real: print i.type, "at ref:", i.ref_span, " other ", i.other_span
 * 1) Main Program starts here