De Novo Genome Assembly Using Kmer Index Labels
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Solution Overview
Problem
Current genomic sequencing methods using reference genomes are prone to errors, particularly in mapping insertions and deletions, and traditional de novo assembly techniques are inefficient for large-scale genome assembly.
Innovation Solution
The method involves labeling nucleic acid molecules with unique identifiers to track their origin, using mate pair information, and creating kmer indexes to align and extend contigs, allowing for accurate de novo assembly by identifying overlapping reads and polymorphic loci to build haploid seeds and extend contigs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mapping to reference genome is used, then alignment speed is improved, but accuracy deteriorates due to bias and errors in identifying insertions and deletions
Solution Approach 1:
The genome assembly process is segmented into local de novo assembly for problematic regions and reference-based mapping for other regions. This allows each method to be applied where it is most effective, resolving the contradiction between speed and accuracy.
Solution Approach 2:
A hybrid approach is introduced as an intermediary between pure reference mapping and pure de novo assembly. The method uses reference genome to guide assembly in reliable regions while performing local de novo assembly in problematic regions, combining the advantages of both approaches.
2Measurement precision
If local de novo assembly is used for problematic regions, then accuracy is improved, but productivity deteriorates when applied to entire genome
Solution Approach 1:
The genome is segmented into problematic regions requiring local de novo assembly and non-problematic regions suitable for reference-based mapping. This segmentation allows accurate local assembly to be applied only where necessary, maintaining productivity while improving accuracy.
Solution Approach 2:
Instead of applying full de novo assembly to the entire genome, the method applies partial de novo assembly only to specific problematic regions identified through initial reference-based mapping, reducing computational burden while maintaining accuracy where needed.
3Productivity
If reference genome mapping is used, then productivity is improved, but reliability deteriorates due to bias in results
Solution Approach 1:
The assembly process is segmented into reference-based mapping for high-productivity regions and local de novo assembly for unbiased regional analysis. This ensures reliability in critical regions while maintaining overall productivity.
Solution Approach 2:
Different assembly strategies are applied to different regions based on their specific characteristics. Problematic regions receive localized de novo assembly treatment for unbiased results, while other regions use efficient reference-based mapping, optimizing both reliability and productivity locally.
Data Source
AI summary
Techniques perform de novo assembly. The assembly can use labels that indicate origins of the nucleic acid molecules. For example, a representative set of labels identified from initial reads that overlap with a seed can be used. Mate pair information can be used. A sequence read that aligns to an end of a contig can lead to using the other sequence read of a mate pair, and the other sequence read can be used to determine which branch to use to extend, e.g., in an external cloud or helper contig. A kmer index can include labels indicating an origin of each of the nucleic acid molecules that include each kmer, memory addresses of the reads that correspond to each kmer in the index, and a position in each of the mate pairs that includes the kmer. Haploid seeds can also be determined using polymorphic loci identified in a population.