Contents
What is read assembly?
In bioinformatics, sequence assembly refers to aligning and merging fragments from a longer DNA sequence in order to reconstruct the original sequence. Typically the short fragments, called reads, result from shotgun sequencing genomic DNA, or gene transcript (ESTs).
What genes assemble?
Genome assembly refers to the process of taking a large number of short DNA sequences and putting them back together to create a representation of the original chromosomes from which the DNA originated.
How do you assemble a genome?
Plan compute resources accordingly.
- Investigate the properties of the genome you study. Every assembly or annotation project is different.
- Extract high quality DNA.
- Choose an appropriate sequencing technology.
- Estimate the necessary computational resources.
- Assemble your genome.
What are gene reads?
In DNA sequencing, a read is an inferred sequence of base pairs (or base pair probabilities) corresponding to all or part of a single DNA fragment. A typical sequencing experiment involves fragmentation of the genome into millions of molecules, which are size-selected and ligated to adapters.
What is a good assembly?
A good assembly should be in as many pieces as the original genetic elements they represent (one contig – one chromosome) but to allow gene calling, genome alignments single base accuracy is also essential. However, it may also be useful to use annotation tools to assess whether genes can be called correctly.
How is genome assembly performed from sequence reads?
Genome assembly from sequence reads is an algorithm-driven automated process. DNA-sequence-assembly programs have utilized sequence overlaps for sequence assembly in correct order. The computational aspect of assembly algorithms is beyond the scope of this book.
Can a reference guided assembler favor known genes?
Some reference-guided assemblers can also use the exon-intron annotation of known transcripts as an optional guide, allowing them to favor known genes where possible.
Is it possible to assemble the human genome from a short read?
The Overlap-Layout-Consensus strategy used to assemble the human genome sequence from Sanger sequencing reads (500 to 900 nt in length) is not feasible for assembly from short reads (50 to 150 nt in length).
How are short reads used in transcriptome assembly?
Reads of this length usually span no more than two exons, except in cases of very small exons. By assembling the short reads, we can reconstruct full-length transcripts and identify novel genes and gene isoforms. There are two main approaches to transcriptome assembly: de novo and reference-guided.