Thursday, November 23, 2006

Human Genome and Global Variation

A new study in today's issue of Nature (available free here) suggests that there can be significant genetic differences between people. These differences involve what are called 'copy-number variants'.

You can learn more about CNVs, and their potential role in the development of disease, by taking a look at the Copy Number Variation Project site at the Sanger Institute.

Here is the abstract of the new study in Nature:

"Global variation in copy number in the human genome"

Copy number variation (CNV) of DNA sequences is functionally significant but has yet to be fully ascertained. We have constructed a first-generation CNV map of the human genome through the study of 270 individuals from four populations with ancestry in Europe, Africa or Asia (the HapMap collection). DNA from these individuals was screened for CNV using two complementary technologies: single-nucleotide polymorphism (SNP) genotyping arrays, and clone-based comparative genomic hybridization. A total of 1,447 copy number variable regions (CNVRs), which can encompass overlapping or adjacent gains or losses, covering 360 megabases (12% of the genome) were identified in these populations. These CNVRs contained hundreds of genes, disease loci, functional elements and segmental duplications. Notably, the CNVRs encompassed more nucleotide content per genome than SNPs, underscoring the importance of CNV in genetic diversity and evolution. The data obtained delineate linkage disequilibrium patterns for many CNVs, and reveal marked variation in copy number among populations. We also demonstrate the utility of this resource for genetic disease studies.

News@Nature also has an overview of the findings here. That story contains a useful "Same But Different" summary chart with the following information which is useful to have on hand:

3,080 million 'letters' of DNA in the human genome

22,205 genes, by one recent estimate

10 million single-letter changes (SNPs) — that's only 0.3% of the genome

1,447 copy-number variants, covering a surprisingly large 12% of the genome

About 99.5% similarity between two random people's DNA