Humans show big DNA differences

LONDON: DNA comparisons: Gains (red), losses (yellow), the same (green). Scientists have shown that our genetic code varies between individuals far more than was previously thought.

A UK-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.

A great many of these variations are in areas of the genome that would not damage our health, Matthew Hurles and colleagues told the journal Nature.

But others are - and can be shown to play a role in a number of disorders.

To date, the investigation of the human genome has tended to focus on very small changes in DNA that can have deleterious effects - at the scale of just one or a few bases, or “letters”, in the biochemical code that programs cellular activity.

And for many years, scientists have also been able to look through microscopes to see very large-scale abnormalities that arise when whole DNA bundles, or chromosomes, are truncated or duplicated.

But it is only recently that researchers have developed the molecular “tools” to focus on medium-scale variations of the code - at the scale of thousands of DNA letters.

This analysis of so-called copy number variation (CNV) has now revealed some startling results.

It would seem the assumption that the DNA of any two humans is 99.9% similar in content and identity no longer holds.

The double-stranded DNA molecule is held together by chemical components called bases Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G)

These “letters” form the “code of life”; there are about 2.9 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes

Written in the DNA are about 20-25,000 genes which human cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies

The researchers were astonished to locate 1,447 CNVs in nearly 2,900 genes, the starting “templates” written in the code that are used by cells to make the proteins which drive our bodies. This is a huge, hitherto unrecognised, level of variation between one individual and the next.

Complete text linked below:

Source:
Humans show big DNA differences
The News International