Biology

How radiation can alter the genetics of many future generations.

 

Events like those in Chernobyl and Fukushima, make us reconsider the safety of radiation. A part of the population will inevitably be exposed to increased amounts of radiation due to their profession. But there are also other creatures that live in the environments we accidentally create and those organisms are perfect for testing how radiation can affect living organisms. There have been many studies in the affected areas, in the exclusion zones where plants and animals still live.

The problem with radiation is that it can damage DNA. DNA gets damaged pretty often in our bodies and our cells are great at fixing it. Evolution relies on those small changes the DNA has to mutate. Some mutations will be good, some bad, the individuals with the good ones survive reproduce etc. and the ones with the bad get extinct. Does accelerating mutations, accelerate evolution though?

In our genome there are sections, called transposons, or transposable elements, that are more susceptible to mutations and can change positions in the genome. Such elements allow for new evolutionary traits and many studies show that they are actually critical for evolution.

So, again… how does evolution go in such areas? Are animals any different?

First of all there are a lot less animals there. Radiation causes tumours that kill part of the population and then other parts may become unable to reproduce. Furthermore, there have been mutations in easily observable characteristics, like colour in insects elitra for example, that cause different patterns or sometimes even colours. Life can adapt to most environments, this can be seen from extremophiles, that survive in extreme conditions. DNA can be damaged by many things. From what we have seen i wouldn’t say that evolution is accelerated in areas with increased radiation compared to other extreme areas (heat, toxic amounts of minerals etc, cold, lack of nutrients). Extreme situations cause damage, damage causes change and change can be either good or bad. It takes time for a significant change but it eventually happens.

Take an animal away from radiation. Will it have mutated children?

From the evidence we have they will probably have fewer children, and less healthy children.

Mutations can affect gametes too, so less sperm will have a stable genome to successfully create a healthy embryo to be born. Then if born there are still mutations. It will be interesting for future studies to focus on whether the same mutation present in parent are also present in children but that can be challenging to prove. For now we know though that animals seem to mutate and appear to be evolving to adapt to their environment. Animals temporarily exposed to radiation have a chance to mutate and carry it to their offspring. When re-introduced to a healthy environment such changes may lead to an advantage over “normal” species and a change in the course of evolution. This may even lead to invasive species, or invasive variants of a species.

This proves that we certainly need to be more careful with our ecosystems and that nature is really amazing.

Sources: The genomic substrate for adaptive radiation in African cichlid fish, Transposons passively and actively contribute to evolution of the two-speed genome of a fungal pathogen, Genomic instability in haematopoietic cells of F1 generation mice of irradiated male parents, In vitro fertilization rate of mouse oocytes with spermatozoa from the F1 offspring of males irradiated with 1.0 Gy 137Cs γ-rays, Intergenerational effects of chemotherapy on fecundity: both male and female children born to women exposed to chemotherapy have fewer children, Faster Development Covaries with Higher DNA Damage in Grasshoppers (Chorthippus albomarginatus) from Chernobyl, Effect of ionizing radiation on transgenerational appearance of p un reversions in mice

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