FindSynteny {DECIPHER} | R Documentation

## Finds Synteny in a Sequence Database

### Description

Finds syntenic blocks between groups of sequences in a database.

### Usage

    FindSynteny(dbFile,
                tblName = "Seqs",
                identifier = "",
                useFrames = TRUE,
                alphabet = AA_REDUCED[[1]],
                geneticCode = GENETIC_CODE,
                sepCost = 0,
                gapCost = -0.01,
                shiftCost = 0,
                codingCost = 0,
                maxSep = 2000,
                maxGap = 5000,
                minScore = 30,
                dropScore = -100,
                maskRepeats = TRUE,
                allowOverlap = TRUE,
                storage = 0.5,
                processors = 1,
                verbose = TRUE)

### Arguments

`dbFile` | A SQLite connection object or a character string specifying the path to the database file.
`tblName` | Character string specifying the table where the sequences are located.
`identifier` | Optional character string used to narrow the search results to those matching a specific identifier. If `""` then all identifiers are selected. Repeated identifiers will find synteny between a sequence and itself, while blocking identical positions from matching in both sequences.
`useFrames` | Logical specifying whether to use 6-frame amino acid translations to help find more distant hits. Using the `alphabet` is helpful when the genome is largely composed of coding DNA. If `FALSE` then faster but less sensitive to distant homology.
`alphabet` | Character vector of amino acid groupings used to reduce the 20 standard amino acids into smaller groups. Alphabet reduction helps to find more distant homologies between sequences. A non-reduced amino acid alphabet can be used by setting `alphabet` equal to `AA_STANDARD`.
`geneticCode` | Either a character vector giving the genetic code to use in translation, or a list containing one genetic code for each identifier. If a list is provided then it must be named by the corresponding identifiers in the database.
`sepCost` | Cost per nucleotide separation between hits to apply when chaining hits into blocks.
`gapCost` | Cost for gaps between hits to apply when chaining hits into blocks.
`shiftCost` | Cost for shifting between different reading frames when chaining reduced amino acid hits into blocks.
`codingCost` | Cost for switching between coding and non-coding hits when chaining hits into blocks.
`maxSep` | Maximal separation (in nucleotides) between hits in the same block.
`maxGap` | The maximum number of gaps between hits in the same block.
`minScore` | The minimum score required for a chain of hits to become a block. Higher values of `minScore` are less likely to yield false positives.
`dropScore` | The change from maximal score required to stop extending blocks.
`maskRepeats` | Logical specifying whether to “soft” mask repeats when searching for hits.
`allowOverlap` | Logical specifying whether to permit blocks to overlap on the same sequence.
`storage` | Excess gigabytes available to store objects so that they do not need to be recomputed in later steps. This should be a number between zero and a (modest) fraction of the available system memory. Note that more than `storage` gigabytes may be required, but will not be stored for later reuse.
`processors` | The number of processors to use, or `NULL` to automatically detect and use all available processors.
`verbose` | Logical indicating whether to display progress.

### Details

Long nucleotide sequences, such as genomes, are often not collinear or may be composed of many smaller segments (e.g., contigs). `FindSynteny` searches for “hits” between sequences that can be chained into collinear “blocks” of synteny. Hits are defined as k-mer exact nucleotide matches or k-mer matches in a reduced amino acid alphabet (if `useFrames` is `TRUE`). Hits are chained into blocks as long as they are: (1) within the same sequence, (2) within `maxSep` and `maxGap` distance, and (3) help maintain the score above `minScore`. Blocks are extended from their first and last hit until their score drops below `dropScore` from the maximum that was reached. This process results in a set of hits and blocks stored in an object of class “Synteny”.

### Value

An object of class “Synteny”.

### Note

`FindSynteny` is intended to be used on sets of sequences with up to ~100 million nucleotides total per identifier. For this reason, better performance can sometimes be achieved by assigning a unique identifier to each chromosome belonging to a large genome.

### Author(s)

Erik Wright eswright@pitt.edu

### See Also

`AlignSynteny`, `Synteny-class`

### Examples

    db <- system.file("extdata", "Influenza.sqlite", package="DECIPHER")
    synteny <- FindSynteny(db)
    synteny
    pairs(synteny) # scatterplot matrix

[Package DECIPHER version 2.20.0 Index]