Since the Chernobyl nuclear disaster in 1986, something has concerned scientists: can exposure to radiation leave marks in someone’s DNA that are passed on to their children? For decades, this idea was mainly focused on visible diseases, but a new study published in Scientific Reports analyzes something more precise: microscopic changes in genetic material. So, let’s find out more about this study.
How the study was designed
Researchers compared three groups:
- 130 children of workers involved in the cleanup after the Chernobyl accident.
- 110 children of former German military radar operators who were likely exposed to scattered radiation during service.
- 1,275 children of parents with no known history of ionizing radiation exposure.
All participants underwent full genome sequencing. First, researchers confirmed that the total number of isolated mutations per generation was similar across groups and followed the expected pattern related to paternal age. No significant differences were found in overall mutation counts.
What happens to DNA when there’s radiation?
Ionizing radiation can interact directly to DNA inside our cells. DNA is like the body’s instruction manual. When radiation hits it, several types of damage can occur:
- Breaks in one or both strands of the DNA molecule.
- Chemical changes in the genetic bases.
- Loss of small pieces of DNA.
One of the most serious forms of damage is a double-strand break, when both strands of DNA are broken at the same time. Often, teh body’s repair systems to fix this damage work well, but sometimes the repair process makes mistakes and when that happens, permanent changes called mutations can remain. Radiation can also cause indirect damage by creating highly reactive molecules inside cells, which then attack the DNA.
If these mutations happen in normal body cells, they only affect the person who was exposed. But if they occur in the cells that make sperm or eggs, the changes can be passed down to their children.
Specific mutations examined
Every generation naturally carries new mutations called “de novo” mutations, which are normal and part of human biology. In fact, it is already known that paternal age plays a role: the older the father at conception, the more isolated new mutations tend to appear in the child.
However, this study focuses on clustered de novo mutations (cDNMs).A cluster is defined as at least two new mutations that occur very close together in the genome, within 20 base pairs of each other.Instead of scattered changes across DNA, these are small groups of mutations concentrated in a tiny region.
More clusters in children of exposed fathers
In total, 1,989 mutation clusters were detected across 1,515 descendants. The average number of clusters per child was:
- 0.88 in the non-exposed group.
- 1.48 in the radar group.
- 2.65 in the Chernobyl group.
In the Chernobyl group, researchers saw that children had more mutation clusters when their fathers had been exposed to higher levels of radiation. For the radar group, the same pattern was there but not as strong, probably because the radiation levels were lower and it was harder to estimate exposure from so long ago.
Health
The researchers examined whether the clustered mutations affected protein-coding regions of the genome or were associated with reported illnesses in the participants. They found no evidence that these clusters were linked to specific diseases in the children studied.
Limitations
The authors acknowledge several limitations:
- The amount of radiation that the radar operators were exposed to was estimated by looking back at old records.
- Clustered mutations have a higher rate of false positives compared to isolated mutations.
- Even for the Chernobyl workers, there is still some uncertainty because many years passed between the exposure and when their children were conceived.
- Not all detected clusters could be experimentally validated.
Despite these limitations, the researchers state that this is the first study to provide direct evidence of a measurable transgenerational effect of prolonged paternal exposure to low doses of ionizing radiation in the human genome.