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For more than 150 years, Charles Darwin’s theory of evolution has been the consensus in biology. He published his theory of variation and natural selection in the mid-19th century, which assumed that species carry their own specific characteristics and pass them along to their offspring. New or modified attributes occur by natural variations and only prevail if they lead to better chances of individual survival. However, Darwin’s idea contradicted distinguished naturalist Jean-Baptiste Lamarck, who postulated that offspring inherit characteristics that are actively acquired by earlier generations. A vivid example of this theory is the giraffe. Lamarck believed that giraffes evolved through the action of continuously stretching their necks to get food from ever high trees in the African steppe, a characteristic that was then inherited by future generations. In other words, the more giraffes stretched for food, the longer the necks of subsequent generations became.
Gregor Mendel's findings, which described genes for the first time, supplemented and confirmed Darwin’s conclusions. Darwin’s theory and Mendel’s principles of heredity have been the status quo in genetics since then, while Lamarck’s theory was consigned to the dustbin of history.
It’s much more than just our genetic code
Research over past years indicates that we may have to exhume Lamarck’s theory however.
We carry about 20,000 identical genes in every cell of our body. Together, they form our genetic blueprint. But the human body has around 200 different cell types, all derived from one kind of stem cell. A specific gene regulation system is the only obvious explanation for this variability. This mechanism is called epigenetics, which refers to a process that coordinates how and to what extent gene information is used in each cell. Epigenetic changes regulate the gene expression while the DNA sequence, our genetic code, remains unaffected.
Small appendages do the job
Epigenetics functions as a 2nd information level of the DNA. Small molecules, the methyl groups, bind to the DNA and fold it in a specific way. This more or less opens up the genes to access by the enzymes, which translate them into proteins. The DNA-methylation patterns are passed from one cell generation to the next, thus guaranteeing that all cells of an organ or with a specific function produce only new cells with the same identity. These patterns also allow the body to interact with the environment and respond to changing influences in a flexible manner. Nutrition and stress can alter the epigenetic pattern for instance.
What parents may pass on to their kids
This begs the question, to what extent are epigenetic factors passed from one human generation to the next? For decades, the genetic gospel held that the information parents pass on to their children is defined by their DNA sequences. Increasing evidence suggests that epigenetic factors are inherited as well. Genes appear to have a multi-generational memory. Recent studies demonstrate that parents with high-fat diets can influence the metabolism of their children and even their grandchildren. Another example is stress. Babies whose mothers were abused during pregnancy developed long-lasting epigenetic changes that were detectable until their teen years.
Epigenetics has the potential to offer diverse opportunities for the innovative treatment of diseases. The idea that scientists could one day cure specific illnesses before an outbreak by simply modulating the epigenetic patterns that are identified as the cause is not too far-fetched. Even cancer treatment could benefit. The targeted methylation of cancerogenic DNA sequences could be used to deactivate oncogenes, thus killing the cells or stopping them from propagating.
Much work lies ahead of us before we can fully understand epigenetic mechanisms and their effects. In the end, we may discover that genetics is simply a mixture of Darwin’s and Lamarck’s concepts.