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Amemiya and his co-workers became suspicious that the lamprey's genome structure and composition was changing during development when they heard rumors lamprey genome sequences efforts were being complicated by genome fragmentation. They speculated that this might be due to genome rearrangements similar to those described for the hagfish, a chordate and superficially similar organism.

To test this, the researchers compared germ line and somatic tissues from sea lamprey caught in Lake Michigan.

Indeed, they found that the genome was larger in sperm (germ line cells) than in adult blood nuclei (somatic cells), even within the same individual. The sperm cells also contained more DNA than kidney and liver cells, which both had similar DNA content to red blood cells. Overall, the researchers noted, sperm genomes contained some 20 percent more DNA than adult cells such as red blood cells.

Over the last several years, genome-wide association studies have become the primary method for identifying variations associated with human disease, but the approach has shortcomings that are leading some in the genomics community to push more aggressively into the post-GWAS era.

At Cambridge Healthtech Institute's Genomic Tools and Technologies Summit held here this week, many speakers noted that even though GWA studies have linked hundreds of common SNPs to disease, these variants account for only a very small portion of disease heritability, which has raised doubts over their clinical value. A number of talks focused on two key alternatives to GWAS: the discovery of rare variants, as opposed to common variants, with a role in disease; and an increasing focus on copy number variants rather than SNPs.

"GWAS was never meant to substitute for fine genomic sequencing," but rather to identify regions of linkage disequilibrium in the genome that warrant further study

Lupski said that efforts like the 1000 Genomes Project will likely produce valuable information that will drive improvements in the use of sequencing for CNV detection. "It's coming along," he said. "I think this will be solved."