Nanguiano Week 4

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Transcription and Translation “Taken to the Next Level”

  • First, I needed to log in to my LMU CS account to access the data used in this weeks assignment.
ssh nanguia1@lion.lmu.edu
  • Next, I needed to enter the folder that I'd created for the class, and create a new folder for this week's assignment.
cd biodb
mkdir week4
  • Next, I moved into Dondi's directory so I could obtain the file required for the assignment - infA-E.coli-K12.txt.
cd ~dondi/xmlpipedb/data
cp infA-E.coli-K12.txt ~nanguia1/biodb/week4
  • Then, I moved into my directory to prepare to do the assignment.
cd ~nanguia1/biodb/week4

For each of the following questions pertaining to this gene, provide (a) the actual answer, and (b) the sequence of text-processing commands that calculates this answer. Specific information about how these sequences can be identified is included after the list of questions.

Modify the gene sequence string so that it highlights or “tags” the special sequences within this gene, as follows (ellipses indicate bases in the sequence; note the spaces before the start tag and after the end tag):

  • -35 box of the promoter 
    ... <minus35box>...</minus35box> ...
    • First, I knew I needed to identify the sequence that I'd be looking for within the file. The week 4 assignment indicated that the consensus sequence for the -35 promoter sequence is tt[gt]ac[at]. In thus, I knew I needed to plug this sequence into sed in order to filter for this sequence. Because I wanted a single replacement of one sequence, I knew that sed s//g would be the best option. My first theory was to try for sed s/tt[gt]ac[at]/ & /g, to put a space on either side of the sequence. This would test whether or not it was finding the sequence correctly, before I put in the tag.
    • I tested using the command cat infA-E.coli-K12.txt | sed "s/tt[gt]ac[at]/ & /g". However, this command did not work, since it changed every single one that appeared, not just the first! Since I only wanted the first one to be changed, I did some research to find out how to change the first iteration using sed. Using this link from Stack Overflow, I learned that the /g in the command was indicating to change every single iteration. Changing it to /1 would cause it to change only the first iteration! Running cat infA-E.coli-K12.txt | sed "s/tt[gt]ac[at]/ & /1" resulted in the output I expected. As a result, all that was left was to find the first and last space and replace then with the starting and ending tags.
    • However, this ended up being harder than expected. Because </minus35box> had a / key, sed interpreted that as the end of the input. The forward slash would need to be escaped in order for sed to treat it not as a part of the command, but rather as a string. I knew that in other command line arguments, a backslash placed before the offending character would escape the character, allowing it to be read as a character. This held true for the sed command as well. The final command and output was as follows: 
cat infA-E.coli-K12.txt | sed "s/tt[gt]ac[at]/ <minus35box>&<\/minus35box> /1"

ttttcaccacaagaatgaatgttttcggcacatttctccccagagtgttataattgcggtcgcagagttggttacgctcattaccccgctgccgataagg 
aatttttcgcgtcaggtaacgcccatcgtttatctcaccgctcccttatacgttgcgcttttggtgcggcttagccgtgtgttttcggagtaatgtgccga
acctgtttgttgcgatttagcgcgcaaatc <minus35box>tttact</minus35box> tatttacagaacttcggcattatcttgccggtt
caaattacggtagtgataccccagaggattagatggccaaagaagacaatattgaaatgcaaggtaccgttcttgaaacgttgcctaataccatgttc
cgcgtagagttagaaaacggtcacgtggttactgcacacatctccggtaaaatgcgcaaaaactacatccgcatcctgacgggcgacaaagtgact
gttgaactgaccccgtacgacctgagcaaaggccgcattgtcttccgtagtcgctgattgttttaccgcctgatgggcgaagagaaagaacgagta
aaaggtcggtttaaccggcctttttattttat
  • -10 box of the promoter 
    ... <minus10box>...</minus10box> ...
    • Using what I had learned from the previous problem, as well as the hint from the week 4 assignment that indicated that the -10 box was located at [ct]at[at]at), I began to formulate the command. Upon running the command to test to make sure that the sequence was being found correctly (cat infA-E.coli-K12.txt | sed "s/[ct]at[at]at/ & /g", I was surprised to find that there was a match both before and after the location that had been found for the minus 35 box. Knowing that that -10 box comes after the -35 box, and there should be around 17 nucleotides between them, I knew that this time I could not simply change the first match, since the first match would not be correct. It would be the second match that would be correct. The final command and output to display the -10 box was as follows:
cat infA-E.coli-K12.txt | sed "s/[ct]at[at]at/ <minus10box>&<\/minus10box> /2"

ttttcaccacaagaatgaatgttttcggcacatttctccccagagtgttataattgcggtcgcagagttggttacgctcattaccccgctgccgataagg
aatttttcgcgtcaggtaacgcccatcgtttatctcaccgctcccttatacgttgcgcttttggtgcggcttagccgtgtgttttcggagtaatgtgccgaa
cctgtttgttgcgatttagcgcgcaaatctttacttatttacagaacttcgg <minus10box>cattat</minus10box> cttgccggttcaa
attacggtagtgataccccagaggattagatggccaaagaagacaatattgaaatgcaaggtaccgttcttgaaacgttgcctaataccatgttccgc
gtagagttagaaaacggtcacgtggttactgcacacatctccggtaaaatgcgcaaaaactacatccgcatcctgacgggcgacaaagtgactgttg
aactgaccccgtacgacctgagcaaaggccgcattgtcttccgtagtcgctgattgttttaccgcctgatgggcgaagagaaagaacgagtaaaagg
tcggtttaaccggcctttttattttat
    • Combined with the code for the minus 35 box, the output is as follows: 
cat infA-E.coli-K12.txt | sed "s/tt[gt]ac[at]/ <minus35box>&<\/minus35box> /1" | sed "s/[ct]at[at]at/ <minus10box>&<\/minus10box> /2"

ttttcaccacaagaatgaatgttttcggcacatttctccccagagtgttataattgcggtcgcagagttggttacgctcattaccccgctgccgataaggaa
tttttcgcgtcaggtaacgcccatcgtttatctcaccgctcccttatacgttgcgcttttggtgcggcttagccgtgtgttttcggagtaatgtgccgaacctg
tttgttgcgatttagcgcgcaaatc <minus35box>tttact</minus35box> tatttacagaacttcgg <minus10box>cattat</
minus10box> cttgccggttcaaattacggtagtgataccccagaggattagatggccaaagaagacaatattgaaatgcaaggtaccgttcttg
aaacgttgcctaataccatgttccgcgtagagttagaaaacggtcacgtggttactgcacacatctccggtaaaatgcgcaaaaactacatccgcatcct
gacgggcgacaaagtgactgttgaactgaccccgtacgacctgagcaaaggccgcattgtcttccgtagtcgctgattgttttaccgcctgatgggcga
agagaaagaacgagtaaaaggtcggtttaaccggcctttttattttat
  • transcription start site 
    ... <tss>...</tss> ...
    • The transcription start site is located at the 12th nucleotide after the first nucleotide of the -10 box. I knew that I first needed to find the -10 box, so I would have to reference the command I used to find the -10 box. However, I knew that I needed to start from the first nucleotide of the box. My first thought was to put a space before the -10 box, so that the character directly before the first nucleotide of the box was a space, using the command sed "s/[ct]at[at]at/ &/2". Then, I would detect this space, and count for 12 characters after it. To test, I put a space directly before the 12th character using the command sed -r "s/ (.){11}/& /g" This correctly displayed the space directly before the 12th character. All that was left was to remove the space before the -10 box, isolate the 12th character and place <tss> before it and </tss> after it in the same way that had been done before. The command and output was as follows:
cat infA-E.coli-K12.txt | sed "s/[ct]at[at]at/ &/2" | sed -r "s/ (.){11}/& <tss>/g" | sed "s/ //1" | sed "s/<tss>./&<\/tss> /g"
ttttcaccacaagaatgaatgttttcggcacatttctccccagagtgttataattgcggtcgcagagttggttacgctcattaccccgctgccgataaggaatt
tttcgcgtcaggtaacgcccatcgtttatctcaccgctcccttatacgttgcgcttttggtgcggcttagccgtgtgttttcggagtaatgtgccgaacctgttt
gttgcgatttagcgcgcaaatctttacttatttacagaacttcggcattatcttgc <tss>c</tss> ggttcaaattacggtagtgataccccagaggatt
agatggccaaagaagacaatattgaaatgcaaggtaccgttcttgaaacgttgcctaataccatgttccgcgtagagttagaaaacggtcacgtggttact
gcacacatctccggtaaaatgcgcaaaaactacatccgcatcctgacgggcgacaaagtgactgttgaactgaccccgtacgacctgagcaaaggccgc
attgtcttccgtagtcgctgattgttttaccgcctgatgggcgaagagaaagaacgagtaaaaggtcggtttaaccggcctttttattttat
  • ribosome binding site 
    ... <rbs>...</rbs> ...
  • start codon 
    ... <start_codon>...</start_codon> ...
  • stop codon 
    ... <stop_codon>...</stop_codon> ...
  • terminator 
    ... <terminator>...</terminator> ...

What is the exact mRNA sequence that is transcribed from this gene? What is the amino acid sequence that is translated from this mRNA?

Links

Nicole Anguiano
BIOL 367, Fall 2015

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