Question

Decide if the following statements best describe map-based genome sequencing, best describe whole-genome shotgun sequencing, or apply equally to both sequencing methods.
a. starts with libraries of large, overlapping DNA fragments
b. starts cloning and sequencing of short, random DNA fragments
c. uses genetic recombination data to help arrange sequences correctly
d. requires sequences to be annotated after contig assembly
e. requires chromosome fragments to overlap for contig assembly
f. requires subcloning of large fragments into smaller clones for sequencing
g. is a better approach for repetitive sequences

1. Map-based genome sequencing
2. Whole-genome shotgun sequencing
3. Both sequencing methods

Answer 1

Answer:

1. Map-based genome sequencing: a; c; f; g

2. Whole-genome shotgun sequencing: b

3. Both sequencing methods: d; e

Explanation:

Map-based genome sequencing is a method that makes use of a reference genome sequence in order to determine the relative position of the DNA fragments before they are sequenced. This method is useful to determine the position of repetitive DNA fragments (for example, duplicated genes, repetitive non-coding regions, etc.) and Transposable Elements. Therefore, map-based genome sequencing is a suitable approach for large genomes (which are usually composed of repetitive sequences). On the other hand, in whole-genome shotgun sequencing, DNA sequences are obtained before the correct order of these DNA fragments is known. In this method, the genome is fragmented randomly into small DNA sequences (between 100 and 1000 base pairs), which are subsequently sequenced through the chain-termination sequencing approach (i.e., Sanger sequencing) and finally ordered by using bioinformatic tools that assemble overlapping reads.