DNA :: Major DNA differences in human genome leads to revised DNA map

A US-led team made a detailed analysis of the DNA found in 270 people and identified vast stretches in their codes to be duplicated or even missing. In 2000, the Human Genome Project unveiled a road map of the six billion chemical bases, or alphabet molecules, that make up the body’s genetic structure called DNA.

Humans are genetically more diverse and the repercussions could be far-reaching for medical diagnosis, new drugs and the tale of human evolution itself, a new research, published in the British journal Nature, suggests. Scientists have shown that our genetic code varies between individuals far more than was previously thought.

The human genome is the genome of Homo sapiens, which is composed of 24 distinct chromosomes with a total of approximately 3 billion DNA base pairs containing an estimated 20,000-25,000 genes.

The Human Genome Project produced a reference sequence of the euchromatic human genome, which is used worldwide in biomedical sciences. The human genome is much more gene-sparse than was initially predicted at the outset of the Human Genome Project, with only about 1.5% of the total length serving as protein-coding exons.

Most studies of human genetic variation have focused on single nucleotide polymorphisms (SNPs), which are substitutions in individual bases along a chromosome. Most analyses estimate that SNPs occur on average somewhere between every 1 in 100 and 1 in 1,000 base pairs in the euchromatic human genome, although they do not occur at a uniform density.

Thus follows the popular statement that “all humans are at least 99% genetically identical”, although this would be somewhat qualified by most geneticists. A large-scale collaborative effort to catalog SNP variations in the human genome is being undertaken by the International HapMap Project.

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