first previous next last contents

Screen Only

This function performs "normal shotgun assembly" without entry and records the percentage mismatch for each matching reading in a file. The file could then be sorted on percentage mismatch and used as a file of file names. i.e. the best matches could be entered first.

[picture]

As explained in normal assembly (see section Normal Shotgun Assembly) the user can select to "Apply masking", and if so, the "Select tags" button will be activated and if it is clicked will bring up a dialogue to allow tag types to be selected. See section Tag Selector.

The "display mode" dialogue allows the type of output produced to be set. "Hide all alignments" means that only the briefest amount of output will be produced. "Show passed alignments" means that only alignments that fall inside the entry criteria will be displayed. "Show all alignments" means that all alignments, including those that fail the entry criteria, are displayed. "Show only failed alignments" displays alignments only for the readings that fail the entry criteria.

When comparing each reading the program looks first for a "Minimum initial match", and for each such matching region found it will produce an alignment. If the "Maximum pads per read" and the "Maximum percent mismatch" are not exceeded the reading will be entered. The maximum pads can be inserted in both the reading and the consensus. If users agree we would prefer to swap the maximum pads criteria for a minimum overlap. i.e. only overlaps of some minimum length would be accepted.

Screening usually works on sets of reading names and they can be read from either a "file" or a "list" and an appropriate browser is available to enable users to choose the name of the file or list. If just a single reading is to be assembled choose "single" and enter the filename instead of the file or list of filenames.

The routine writes the names of all the readings and their alignment scores expressed as percentage mismatches to a "file" or a "list" and an appropriate browser is available to enable users to choose the name of the file or list.

By selecting "Use hidden data" the contigs can be extended using the hidden data close to their ends. To ensure that this additional data is not too poor the program uses the following algorithm. It slides a window of size "Window size for good data scan" along the hidden data for each reading and stops if it finds a window that contains more than "Max dashes in scan window" non-ACGT characters. The data that extends the contig the furthest is added to its consensus sequence. If the user toggles off the use of hidden data the "Window size for good data scan" and "Max number of dashes in scan window" dialogues will be greyed out. Pressing the "OK" button will start the screening process.


first previous next last contents
This page is maintained by James Bonfield. Last generated on 2 Febuary 1999.
URL: http://www.mrc-lmb.cam.ac.uk/pubseq/manual/gap4_24.html