AdapterRemovalAdv

Adapter removal / data cleansing

This node finds an "adapter sequence" within high-through-put sequencing data and removes them. It leaves fragments and information about what caused the removal.

Sequences are compared using simple character based comparison of two sequences, the adpater/query sequence and the target sequence. The query sequence is sliding along the target sequence using the sliding window approach with a step size of 1, starting both from the 5 prime end of the sequences.

If a match has been detected the corresponding part of the target sequence and anything following this sequence on the target sequence will be removed.

A match is in effect, if the fraction of matching base-pairs over the number compared base-pairs is larger than the similarity threshold (see options).

Two bases match if they are the same or if the corresponding quality score for the target base is above the quality threshold (ASCII values are compared).

If the part of the target sequence that is being compared using the sliding window approach is smaller than the query sequence only the overlapping part will be compared and the number of compared bases is therefore also smaller than the length of the query sequence.

If the part of the target sequence that is being compared using the sliding window approach is shorter than "minimum overlap" the sequences don't match.

If the value for "partial comparisons" is greater than "0" (null) the query sequence is clipped from the 5 prime end until "minimum overlap" length is reached. Each such sequences is treated as an independent adapter sequence.