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Genetic building blocks

Making medicines match

Proteins first, genes second

Nuclear explosion at the Nevada Test Site, 1955. Above ground tests were conducted at the site until 1963. Some tests were conducted to improve understanding of plutonium dispersal. As a result, the top 3 to 6 inches of soil is contaminated with plutonium in a 580-acre area known as "Plutonium Valley".
Courtesy Department of Energy.

Germline changes affect sperm, eggs or the cells that make them. Changes in these reproductive cells are passed to future generations, so they are the most serious consequence of artificial releases of radiation.

Map of Kazakhstan showing the Semipalatinsk region, site for years of nuclear testing. Courtesy Department of Energy.

The research was lead by Yuri Dubrova, a geneticist at the University of Leicester in the United Kingdom. Dubrova and his colleagues looked at families that had lived near the Semipalatinsk nuclear test site.

At this God-forsaken land, now in Kazakhstan, the Soviets blew off 470 nuclear tests between 1949 and 1989. The worst source of contamination was atmospheric testing, which was ended in 1963 by an agreement between the United States and the Soviet Union.

The researchers found that only low levels of radioactive contamination remain outside the former test zone.

The study compared three-generation families. Forty came from the test zone with the highest historic exposures to ionizing radiation. A control group of 28 families came from elsewhere in Kazakhstan.

People born before 1948 (before atmospheric testing began) were all exposed to about the same amount of fallout, and their children had 1.8 times more mutations at eight regions of their chromosomes than the control group.

People born between 1950 and 1956 were exposed as youngsters to fallout -- the worst atmospheric tests were held in 1949, 1951, 1953, and 1956. Children of this group had a 1.5-fold increase in chromosome abnormalities.

Age is not healthy to children and other living things
Interestingly, the older the subject in this group, the more abnormal their children's genes. In other words, there was a positive correlation between abnormalities and radiation dose. (Those born in 1950 were exposed to all of the big fallout-producing blasts; those born in 1956 missed the worst fallout.)

Assessments of natural background, nuclear weapons test fallout, accidents, and former processing facilities require surveys of radiation, as is being done here at Semipalatinsk, the former Soviet Union's favorite blasting-ground. Courtesy Department of Energy.

In sum, the scientists wrote their finding reinforced the effectiveness of the first Cold-War arms agreement. "Most important, the negative correlation between the mutation rate and the parental year of birth [among those born between 1950 and 1956] provides experimental evidence for change in human germline mutation rate with declining exposure to ionizing radiation and therefore shows that the Moscow treaty banning nuclear weapon tests in the atmosphere (August 1963) has been effective in reducing genetic risk to the affected population."

Just about every aspect of genetic research is benefiting from the Human Genome Project. Read our coverage.

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