NEW YORK (GenomeWeb News) – An analysis of Craig Venter’s genome published in this week’s issue of PLoS Biology indicates that there is more variation in the human genome than indicated by previous studies.
Researchers at the J. Craig Venter Institute, the Hospital for Sick Children in Toronto, and the University of California San Diego contributed to the effort to sequence and analyze the so-called “HuRef” genome, which is the first completed diploid human genome to be published.
The analysis revealed that there is a high degree of variation between the two chromosomal copies of an individual, and that genetic variation between two individuals is up to seven times higher than previously estimated.
In addition, the study found that while SNPS make up 88 percent of genomic variation events, lesser-studied variants such as insertions and deletions actually account for almost 74 percent of all variant nucleotides — a “surprising number,” according to JCVI.
"With this publication, we have shown that human-to-human variation is more than seven-fold greater than earlier estimates, proving that we are in fact very unique individuals at the genetic level," Venter said in a statement.
The team assembled the HuRef genome of over 2.8 billion base pairs from more than 20 billion base pairs. JCVI said it covered the genome 7.5 times, which allowed for over 96 percent coverage of the two parental genomes.
The researchers used information from a draft of Venter's genome that Celera had originally generated in its effort to sequence the human genome that it published in 2001. Venter’s genome made up around 60 percent of the Celera genome, which was a consensus assembly of five individuals. The team also used additional whole-genome shotgun sequencing to generate an additional 32 million more sequences for the HuRef genome.
The ability to compare two chromosomes within an individual will enable new findings, JCVI said.
The study's lead author, Sam Levy, a JCVI senior scientist, said new methodologies have enabled the team to characterize "a wide variety of individual genetic variation," affording "an unprecedented opportunity to study the prevalence and impact of these DNA variants on traits and diseases in human populations."
The diploid HuRef genome will also enable improved haplotype assemblies, which could help scientists find variants that would explain and help predict disease in individuals, JCVI said.