Damage to DNA and its repair
The breaking of DNA and its repair is a completely natural process in the cells of the body. The cells’ production of energy is mainly responsible for the damage to the DNA.
Fortunately, the cells also contain enzymes that help protect and repair the DNA.
Sometimes, if the DNA is not repaired correctly, errors occur in the genetic code. These errors are also called mutations, and they contribute to our aging process.
Sperm cells cannot repair DNA
Unlike the other cells in the body, sperm cells cannot repair DNA. Therefore, it is essential that the sperm cell’s DNA is well packaged to protect it from damage.
The sperm cell has to swim in order to reach and fertilise the egg for which it needs a huge amount of energy. If the DNA is fragile, it can get damaged before the egg has been fertilised.
Fortunately, the egg has the necessary enzymes to repair minor damage to the sperm cell’s DNA. The egg can repair damage as long as it only involves a break to one of the DNA-strands. However, if there are many breaks, there is a risk of mutations, which will affect the foetus.
Major damage to the sperm’s DNA in which both DNA-strands have been broken (i.e., fragmentation) almost always results in the death of the fertilised egg. In these cases, pregnancy won’t occur, or a miscarriage will take place.
Fragile vs fragmented DNA
About 20 years ago, the common conception was that the man’s fertility depended on the number of sperm cells produced and whether they could swim. However, the identification of DNA fragmentation represented a paradigm shift in our understanding of the man’s fertility.
At first, scientists thought that some sperm cells contained intact DNA while others contained fragmented DNA. Therefore, there was a huge interest in selecting sperm cells without fragmented DNA.
In 2010, there was another paradigm shift, which shed new light on this area: in reality, DNA fragmentation occurs because the sperm cell’s DNA is fragile.
Scientists thought that they should focus on the fragmented DNA, but this was just the tip of the iceberg as the problem was fragile DNA, which represented the part of the iceberg that is under the surface.