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Babak Hossein Khalaj

Publications and source records attributed to Babak Hossein Khalaj.

2 recordsLinked to original sources

Breaking Lander-Waterman’s Coverage Bound

Lander-Watermans coverage bound establishes the total number of reads required to cover the whole genome of size G bases. In fact, their bound is a direct consequence of the well-known solution to the coupon collectors problem which proves that for such genome, the total number of bases to be sequenced should be O (G ln G). Although the result leads to a tight bound, it is based on a tacit assumption that the set of reads are first collected through a sequencing process and then are processed through a computation process, i.e., there are two different machines: one for sequencing and one for processing. In this paper, we present a significant improvement compared to Lander-Watermans result and prove that by combining the sequencing and computing processes, one can re-sequence the whole genome with as low as O(G) sequenced bases in total. Our approach also dramatically reduces the required computational power for the combined process. Simulation results are performed on real genomes with different sequencing error rates. The results support our theory predicting the log G improvement on coverage bound and corresponding reduction in the total number of bases required to be sequenced.

Bioinformatics

Meta-aligner: Long-read alignment based on genome statistics

Fast and accurate alignment of long-reads plays an important role in reducing the overall cost of long-read sequencing. In this paper, we propose Meta-aligner, an efficient and accurate long-read aligner that exploits the statistics of reference genome to improve performance in terms of reducing time complexity and achieving significantly higher recall for very noisy and long reads. The first step of algorithm adopts well-known short-read aligners in order to rapidly align a large fraction of reads through a progressive process of aligning read fragments to the reference genome. In the second phase, the remaining reads are handled by simultaneous alignment of all read fragments and a decision making process which exploits the overall information provided by the corresponding mapped fragments. By using this procedure, significant performance improvement is attained in comparison with traditional schemes in the case of PacBio long-reads.

Bioinformatics