Characterization of expressed sequence tag-derived single-nucleotide polymorphisms in the bay scallop Argopecten irradians irradians
Li, R., Ocean Univ. of China, Qingdao | Li, Q. | Kong, L.
We describe herein the discovery of 3905 putative single-nucleotide polymorphisms (SNPs) from the alignment of 4968 sequences in a bay scallop Argopecten irradians irradians expressed sequenced tag (EST) database. The observed frequency of SNPs was estimated at one every 118.2 bp of contig sequences. Thirty of the SNPs were chosen for validation by tetra-primer amplification refractory mutation system-polymerase chain reaction procedure, and 17 of them were polymorphic with minor allele frequency ranging from 0.016 to 0.484. BLASTX gave significant hits for all but one of the 17 genotyped SNP-containing contigs, 11 of which were located in coding regions and all resulted in a synonymous substitution. Parentage simulation demonstrated that SNP markers were more sensitive to the number of parents compared with microsatellites, thus more SNPs were needed to counteract low polymorphism. A table of optimal codons was deduced from the analysis of the A. i. irradians EST dataset to explain the frequency difference for a specific SNP. It seems that the selection of codon usage may be partly responsible for the frequency difference between the two alleles of the coding SNPs. These are the first SNPs developed for the bay scallop and will provide a useful complement to currently available genetic markers.
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