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

From OpenWetWare

Jump to: navigation, search

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: </br> 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:

#find all orfs within the sequences
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]

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

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

#def is_frameshift(mutation, all_orfs):    

#Main Program starts here          
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
    

Personal tools