Section 7-3: Modification of an Existing File or Database Sequence

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This section describes to use sequences which are already available in the GCG environment. WPI users might refer to the WPI chapter for details on how to use sequences in this envoronment. If you want to use sequences which are known in the sequence databases, you do not need to copy these data into your directory but rather use the name of the entry directly - use the local database section for reference.


Subsection 7.3.1

Navigation

If you start the 'seqed' program on an existing file, you will end up directly on the command line. You may go to the command line with a special key combination as depicted below, and you may finally exit the program by typing exit.

The following Figure symbolises the screen of the sequence editing program on the left side, and the commands required to move from one level to the next are indicated with arrows.

 

  
   :                    :
  
   :   (Heading area)   :         
  
   :                    :         ^                    |
  
   :                    :         |                    |
  
                                  | heading <RETURN>   |  <CTRL><D>
  
                                  |                    v
  
   AGCGCTGACAGCTGAGA              |       
  
   ....|....:....|....:..         | ^                  |
  
   (sequence line)                | | <RETURN>         |  <CTRL><D>
  
                                  | |                  v
  
   :                           
  
   (command line)                 ^                    |
  
                                  | seqed              |   exit
  
                                  |                    v
  
  % (system prompt) 
  

  


Subsection 7.3.2

Start of the 'seqed' Program

The program 'seqed' is started by typing its name:

% seqed

You then will be prompted for the name of the sequence you want to modify. Do this by responding to the question

 

  
what file?
  

  
You are now on the sequence line, this mode is the so-called screen mode.


Subsection 7.3.3

Screen Mode Commands

seqed screen mode commands are:

 

  
Symbol    meaning                       action 
  
------------------------------------------------------------------
  
1         (number)                      jump to specified position 
  
-> <-     (arrows)                      move 1 left or right 
  
> <       (larger/smaller)              move 50 left or right
  
10 ->     (number+cursor)               move number left or right
  
/atg      (slash followed by pattern)   jump to pattern
  

  
You might use <CTRL><R> (if screen weird) to refresh the screen. In order to leave the screen mode, type

<CTRL><D>


Subsection 7.3.4

Command Line Mode Commands

seqed command line mode commands are:

 

  
command (example)      command (general)  action 
  
----------------------------------------------------------------------------
  
help                   help               on-line help
  
1,200 Write test.seq   n,m write <file>   write sequence (fragment) to file
  
300 Include test.seq   n include <file>   include new sequence (at pos. 300)                
  
exit                   exit               save work and exit 
  
quit                   quit               cancel work and exit 
  

  
================================= Begin Exercise 3

Another small 'seqed' exercise: Use the 'seqed' program to create a DNA sequence fragment.

Use the sequence editor 'seqed' and view the DNA sequence with the accession number M19311. (You need to give the name as GENEMBL:M19311.) You shall extract the reading frame of this sequence - the start and stop codon can be found in the annotation of this sequence - you will want to seek the CDS (coding sequence) features, to find the desired codons there.

Name the newly created sequence "my2.seq" - we will need this sequence in later exercises.

================================= End Exercise 3


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