Nature vs. nurture: are our characteristics caused by our genetic makeup or our environment and how we were raised? The answer is a combination of both, but there is another factor contributing to our behavioral tendencies: the experiences of our ancestors.
We do not express all of the genes present in our DNA, which is why our liver cells and brain cells function differently although they have the same DNA. The cell needs certain molecules, such as methyl groups or acetyl groups, to activate or “turn on” and transcribe the particular genes needed for that cell and inhibit transcription of other genes not needed. This is called epigenetics: changes caused by modification of gene expression rather than altering the genetic code.
A genetic change is a change in the nucleotide sequence while an epigenetic change adds methyl groups to the DNA molecule without altering the sequence.
When a methyl group attaches to a portion of the DNA, expression of the gene coded for by that portion will be repressed. Without this methyl group, the gene will be expressed.
Epigenetics has gotten a lot of attention from researchers and in scientific journals recently as new information emerges. Siddhartha Mukherjee, a Pulitzer Prize winner and physician, had an article about epigenetics published in the New Yorker in May called "Same but Different." The article has attracted a lot of criticism from geneticists and scientists who say his article put too much emphasis on DNA methylation and ignored the importance of transcription factors in epigenetics. He also argues that epigenetics may provide evidence for Lamarckian evolution, a theory that has been discredited by Darwin.
Epigenetic changes were originally only thought to occur during fetal development, but they can happen in adulthood in response to one’s diet or exposure to chemicals. Surprisingly, these changes can be passed down through generations, inherited like gene mutations along with the rest of our parents’ genetic information.
Epigenetic changes were originally only thought to occur during fetal development, but they can happen in adulthood in response to one’s diet or exposure to chemicals. Surprisingly, these changes can be passed down through generations, inherited like gene mutations along with the rest of our parents’ genetic information.
Amazingly, it was discovered that traumatic experiences like child neglect or drug and alcohol abuse can cause epigenetic changes in the DNA in a person’s brain. A mother’s behavior can cause the attachment of methyl groups or acetyl groups to her child’s DNA, causing an epigenetic change in the child’s heritable genetic information. The altered transcription of genes alters brain function, which is why people cannot “just get over” traumatic experiences from earlier in their life. Their experiences may have caused modifications in their genetic code, through the attachment of methyl groups to their DNA, and to their brain that permanently connect them to feelings of fear and sadness. These experiences leave molecular scars on a person’s DNA which they carry with them and pass down to their children. Behavioral and psychological tendencies are partially inherited, so if your grandfather was neglected as a child, you could inherit a susceptibility to depression. Scientists are trying to find new drugs to wipe clean the damage left by our ancestors on our DNA, but it is difficult since positive experiences can cause positive epigenetic changes as well. They cannot be sure that the drugs would only wipe away the harmful alterations and leave the beneficial ones. For now at least, we must carry the history of our ancestors and their experiences in our own DNA.
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