perl应用：六框阅读翻译DNA序列

生物学知识：

1.六框翻译

??????? 因为DNA为双链,平时从NCBI等里面得到的只是其中的一条链,还有一个互补链没有结出. 先从一条链讲起,如此链为ACGATGCCG....则现在有以下三种读法：第一种，ACG/ATG/CCG.... 第二种，把A看做前面的部分，则为A/CGA/TGC/CG..... 第三种，把AC看做是前面的部分，则为AC/GAT/GCC/G... 只此一条链就有三种读码框。当然，互补链也有其对应的三个读码框，所以两者加起来是六个读码框了。

比如序列：ACGACGACGACGACGACG，可能的读码框就有以下三种:
ACG ACG ACG ACG ACG ACG ACG ACG
CGA CGA CGA CGA CGA CGA CGA CGA
GAC GAC GAC GAC GAC GAC GAC GAC

use strict;  
use warnings;  
  
  
my $dna      ='';  
my $protein  ='';  
my @file_data=( );  
my @filedata;
my $revcom='';


#打开文件 
@filedata  = get_file_data();
#得到序列
$dna       = extract_sequence_from_fasta_data(@filedata);  

#六框阅读翻译

print "n---------------------Reading Frame 1-----------------n";
$protein=translate_frame($dna,1);
print_sequence($protein,70);

print "n---------------------Reading Frame 2-----------------n";
$protein=translate_frame($dna,2);
print_sequence($protein,70);

print "n---------------------Reading Frame 3-----------------n";
$protein=translate_frame($dna,3);
print_sequence($protein,70);

print "n---------------------Reading Frame 4-----------------n";
$protein=translate_frame($dna,4);
print_sequence($protein,70);

print "n---------------------Reading Frame 5-----------------n";
$protein=translate_frame($dna,5);
print_sequence($protein,70);

print "n---------------------Reading Frame 6-----------------n";
$protein=translate_frame($dna,6);
print_sequence($protein,70);

sub get_file_data
{  
	# A subroutine to get data from a file given its filename
	#读取文件的子序列
    my $dna_filename;
	my @filedata;
    print "please input the Path just like this f:\perl\data.txtn";   
    chomp($dna_filename=<STDIN>); 
	open(DNAFILENAME,$dna_filename)||die("can not open the file!");    
	@filedata     = <DNAFILENAME>;  
	close DNAFILENAME;  
	return @filedata;#子函数的返回值一定要记住写
}

sub extract_sequence_from_fasta_data  
{  
    #*******************************************************************  
    # A subroutine to extract FASTA sequence data from an array  
    # 得到其中的序列  
    # fasta格式介绍：  
    # 包括三个部分  
    # 1.第一行中以>开头的注释行，后面是名称和序列的来源  
    # 2.标准单字母符号的序列  
    # 3.*表示结尾  
    #*******************************************************************  
  
    my (@fasta_file_data) =@_;  
    my $sequence =' ';  
    foreach my $line (@fasta_file_data)  
    {  
        #这里忽略空白行  
        if ($line=~/^s*$/)  
        {  
            next;  
        }  
        #忽略注释行  
        elsif($line=~/^s*#/)  
        {  
            next;  
        }  
        #忽略fasta的第一行  
        elsif($line=~/^>/)  
        {  
            next;  
        }  
        else  
        {  
            $sequence .=$line;  
        }  
    }  
    $sequence=~s/s//g;  
    return $sequence;  
}  
  
sub print_sequence  
{  
    # A subroutine to format and print sequence data  
    my ($sequence,$length) = @_;  
    for (my $pos =0; $pos<length($sequence);$pos+=$length)  
    {  
        print substr($sequence,$pos,$length),"n";  
    }  
}  
  
     
  
sub codon2aa     
{     
  
    #第三种方法    
    #也就是运用哈希    
    #我们将所有的密码子作为hash的key，然后将代表的氨基酸作为hash的value    
    #然后进行匹配    
    # codon2aa     
    # A subroutine to translate a DNA 3-character codon to an amino acid     
    # Version 3,using hash lookup     
    my($codon) = @_;     
     
    $codon = uc $codon;#uc=uppercase;lc=lowercase    
                   #也就是大小写转换，uc表示将所有的小写 转换为大写    
               #lc将所有的大写转换为小写    
      
    my(%genetic_code) = (     
         
    'TCA' => 'S',# Serine     
    'TCC' => 'S',# Serine     
    'TCG' => 'S',# Serine     
    'TCT' => 'S',# Serine     
    'TTC' => 'F',# Phenylalanine     
    'TTT' => 'F',# Phenylalanine     
    'TTA' => 'L',# Leucine     
    'TTG' => 'L',# Leucine     
    'TAC' => 'Y',# Tyrosine      
    'TAT' => 'Y',# Tyrosine     
    'TAA' => '_',# Stop     
    'TAG' => '_',# Stop     
    'TGC' => 'C',# Cysteine     
    'TGT' => 'C',# Cysteine     
    'TGA' => '_',# Stop     
    'TGG' => 'W',# Tryptophan     
    'CTA' => 'L',# Leucine     
    'CTC' => 'L',# Leucine     
    'CTG' => 'L',# Leucine     
    'CTT' => 'L',# Leucine     
    'CCA' => 'P',# Proline     
    'CCC' => 'P',# Proline     
    'CCG' => 'P',# Proline     
    'CCT' => 'P',# Proline     
    'CAC' => 'H',# Histidine     
    'CAT' => 'H',# Histidine     
    'CAA' => 'Q',# Glutamine     
    'CAG' => 'Q',# Glutamine     
    'CGA' => 'R',# Arginine     
    'CGC' => 'R',# Arginine     
    'CGG' => 'R',# Arginine     
    'CGT' => 'R',# Arginine     
    'ATA' => 'I',# Isoleucine     
    'ATC' => 'I',# Isoleucine     
    'ATT' => 'I',# Isoleucine     
    'ATG' => 'M',# Methionine     
    'ACA' => 'T',# Threonine     
    'ACC' => 'T',# Threonine     
    'ACG' => 'T',# Threonine     
    'ACT' => 'T',# Threonine     
    'AAC' => 'N',# Asparagine     
    'AAT' => 'N',# Asparagine     
    'AAA' => 'K',# Lysine     
    'AAG' => 'K',# Lysine     
    'AGC' => 'S',# Serine     
    'AGT' => 'S',# Serine     
    'AGA' => 'R',# Arginine     
    'AGG' => 'R',# Arginine     
    'GTA' => 'V',# Valine     
    'GTC' => 'V',# Valine     
    'GTG' => 'V',# Valine     
    'GTT' => 'V',# Valine     
    'GCA' => 'A',# Alanine     
    'GCC' => 'A',# Alanine     
    'GCG' => 'A',# Alanine     
    'GCT' => 'A',# Alanine         
    'GAC' => 'D',# Aspartic Acid     
    'GAT' => 'D',# Aspartic Acid     
    'GAA' => 'E',# Glutamic Acid     
    'GAG' => 'E',# Glutamic Acid     
    'GGA' => 'G',# Glycine     
    'GGC' => 'G',# Glycine     
    'GGG' => 'G',# Glycine     
    'GGT' => 'G',# Glycine     
    );     
     
    if(exists $genetic_code{$codon})     
    {     
        return $genetic_code{$codon};     
    }    
    else    
    {     
     
            print STDERR "Bad codon "$codon"!!n";     
            exit;     
    }     
}     
  
sub dna2peptide  
{  
    my ($dna)=@_;  
    my $protein ='';  
    for (my $i=0; $i<(length($dna)-2);$i+=3)  
    {  
        $protein .=codon2aa(substr($dna,$i,3));  
    }  
    return $protein;#这个词错误找了一晚上，没有返回值，所以结果总是没有内容，以后要引以为戒，子程序一定要有返回值  
}  

sub translate_frame
{
	my ($seq,$start,$end)=@_;
	my $protein;
	
	unless($end)
	{
		$end=length($seq);
	}
	return dna2peptide(substr($seq,$start-1,$end-$start+1));
}