| ## EMBOSS: megamerger

# Program megamerger

## Function

Merge two large overlapping nucleic acid sequences

## Description

megamerger takes two overlapping sequences and merges them into one sequence. It could thus be regarded as the opposite of what splitter does.

The sequences can be very long. The program does a match of all sequence words of size 20 (by default). It then reduces this to the minimum set of overlapping matches by sorting the matches in order of size (largest size first) and then for each such match it removes any smaller matches that overlap. The result is a set of the longest ungapped alignments between the two sequences that do not overlap with each other. If the two sequences are identical in their region of overlap then there will be one region of match and no mismatches.

It should be possible to merge sequences that are Mega bytes long. Compare this with the program merger which does a more accurate alignment of more divergent sequences using the Needle and Wunsch algorithm but which uses much more memory.

The sequences should ideally be identical in their region of overlap. If there are any mismatches between the two sequences then megamerger will still attempt to create a merged sequence, but you should check that this is what you required.

A report of the actions of megamerger is written out. Any actions that require a choice between using regions of the two sequences where they have a mismatch is marked with the word WARNING!. The sequence in these regions is written out in uppercase. All other regions of the output sequence are written in lowercase.

Where there is a mismatch then the sequence that is chosen to supply the region of the mismatch in the final merged sequence is that sequence whose mismatch region is furthest from the start of end of the sequence.

## Usage

Here is a sample session with megamerger, there are many mismatches between these two sequences and the merged sequence should therefore be treated with great caution:

    % megamerger embl:ap000504 embl:af129756
    Merge two large overlapping nucleic acid sequences
    Output sequence [ap000504.merged]:
    Output file [stdout]: report
    Word size [20]:

## Command line arguments

       Mandatory qualifiers:
      [-seqa]              sequence   Sequence USA
      [-seqb]              sequence   Sequence USA
       -wordsize           integer    Word size
      [-outseq]            seqout     Output sequence USA
       -report             outfile    Output report

       Optional qualifiers: (none)
       Advanced qualifiers: (none)
       General qualifiers:
      -help                bool       report command line options. More
                                      information on associated and general
                                      qualifiers can be found with -help -verbose

Mandatory qualifiers | Allowed values | Default
--- | --- | ---
[-seqa] (Parameter 1) | Sequence USA | Readable sequence | Required
[-seqb] (Parameter 2) | Sequence USA | Readable sequence | Required
-wordsize | Word size | Integer 2 or more | 20
[-outseq] (Parameter 3) | Output sequence USA | Writeable sequence | <sequence>.format
-report | Output report | Output file | stdout
Optional qualifiers | Allowed values | Default
(none)
Advanced qualifiers | Allowed values | Default
(none)

## Input file format

Sequence USAs.

## Output file format

A merged sequence is written out.

Where there has been a mismatch between the two sequences, the merged sequence is written out in uppercase and the sequence whose mismatch region is furthest from the edges of the sequence is used in the merged sequence.

The name and description of the first input sequence is used for the name and description of the output sequence. A report of the merger is written out.

A typical report where there are many mismatches, taken from the example above follows:

    # Report of megamerger of: AP000504 and AF129756

    AP000504 overlap starts at 1
    AF129756 overlap starts at 6036

    Using AF129756 1-6035 as the initial sequence

    Matching region AP000504 1-846 : AF129756 6036-6881
    Length of match: 846

    WARNING!
    Mismatch region found:
    Mismatch AP000504 847-847
    Mismatch AF129756 6882-6882
    Mismatch is closer to the ends of AP000504, so use AF129756 in the merged sequence

    Matching region AP000504 848-1794 : AF129756 6883-7829
    Length of match: 947

    WARNING!
    Mismatch region found:
    Mismatch AP000504 1795-1795
    Mismatch AF129756 7830-7830
    Mismatch is closer to the ends of AP000504, so use AF129756 in the merged sequence

    Matching region AP000504 1796-2272 : AF129756 7831-8307
    Length of match: 477

    [many lines removed for brevity]

    Matching region AP000504 97717-97826 : AF129756 103745-103854
    Length of match: 110

    WARNING!
    Mismatch region found:
    Mismatch AP000504 97827-97827
    Mismatch AF129756 103855-103855
    Mismatch is closer to the ends of AP000504, so use AF129756 in the merged sequence

    Matching region AP000504 97828-100000 : AF129756 103856-106028
    Length of match: 2173

    AP000504 overlap ends at 100000
    AF129756 overlap ends at 106028

    Using AF129756 106029-184666 as the final sequence

## Data files

None.

## Notes

If you run out of memory, use a larger wordsize.

## References

None.

## Warnings

None.

## Diagnostic Error Messages

None.

## Exit status

It always exits with status 0.

## Known bugs

None.

## See also

Program name | Description
--- | ---
cons | Creates a consensus from multiple alignments
merger | Merge two overlapping nucleic acid sequences

Compare this with the program merger which does a more accurate alignment of more divergent sequences using the Needle and Wunsch algorithm but which uses much more memory.

A graphical dotplot of the matches used in this merge can be displayed using the program dotpath.

## Author(s)

This application was written by Gary Williams (gwilliam@hgmp.mrc.ac.uk)

## History

Written Aug 2000 by Gary Williams.

## Target users

This program is intended to be used by everyone and everything, from naive users to embedded scripts.

## Comments