Life is not all about genetics

The thing that got me into molecular biology was genetics. In high school I was amazed by the fact that the tiny pieces of DNA in our cells controlled nearly all aspects of an organism. The fact that we could manipulate the DNA sequence and thus manipulate life was a big reason to study molecular biology. Genetics was really awesome. It was life, literally. As I moved on to university I found out that there was more to the story. Life was more than genetics. There was something called epigenetics (meaning over/above genetics). While genetics is the study of genes and it’s sequence, epigenetics is the study of DNA changes that are not due to changes to the DNA sequence. What this means is that the DNA can be altered, chemically, by the attachment of chemical tags known as methyl groups in a process known as DNA methylation (see figure below).

A genetic change (mutation) is when the DNA sequence is altered. An epigenetic change alters the properties of the DNA/gene by the addition of a methyl group (Me) to the DNA but does not alter the sequence. The unmethylated and methylated DNA have identical sequence.

These tags do not alter the DNA sequence, but still have profound effects on the activity of genes. Genes that are methylated are normally turned off. Epigenetics thus controls which genes are turned on or off and therefore controls life. I was really amazed when I was introduced to epigenetics because I had always thought that genetics was everything. Epigenetics was a whole new world.

In contrast to genetic changes (mutations), epigenetic changes are more dynamic. Much of the health effects we see due to our diet and lifestyle are attributed to epigenetics. Green tea for example, which is said to protect us from cancer, contains a molecule called epigallocatechin gallate (EGCG). EGCG has been shown to block methylation of genes that are normally methylated and turned off in cancer. Many genes that are turned off in cancer by methylation are genes that protects us from cancer. So by drinking green tea, we prevent these genes from being turned off and therefore reduce the risk of developing cancer.

Another interesting thing about epigenetics is that it explains the difference between humans and chimpanzees. The DNA of humans and chimpanzees is over 98 % identical, but yet we are so different. How come? Are the last two percent what makes us so different? Scientists have shown that much of the differences between humans and chimpanzees are due to epigenetic and not genetic differences. Some genes that are unmethylated and turned on in humans are methylated and turned off in chimpanzees and vice versa. This generates two completely different organisms with nearly identical genetics. I found this very amazing as a university student because I had thought that genetics was everything. But as I learned, life is not all about genetics.

Green tea protects us from cancer


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