Final answer:
The environment influences gene expression through epigenetics, with factors like early life care having profound impacts on the stress response. Attentive mothering in rats results in lower stress-response gene activation, a relationship also seen in swapped pups, highlighting the significance of nurture over nature.
Step-by-step explanation:
How Does the Environment Affect DNA Expression and Stress Response?
The environment can significantly impact gene expression through a mechanism called epigenetics. This term refers to the changes in gene expression that do not involve alterations to the underlying DNA sequence but can be transmitted to the next generation. For example, environmental factors such as diet, stress, and exposure to toxins can lead to the addition or removal of chemical groups to the DNA or histones, affecting how genes are turned on or off.
Early life care importantly shapes the stress response through epigenetic mechanisms. Studies involving rats have shown that pups with attentive mothers tend to have a lower activation of stress-response genes later in life, which is attributed to the nurturing environment affecting the epigenetic state of these genes. Conversely, pups with inattentive mothers exhibit higher stress gene activation. This influence persists even when pups are swapped at birth, indicating that it is the care received rather than the genetic relationship driving this effect.
In the context of diseases, epigenetic changes can also play a role. For instance, autoimmune diseases are sometimes associated with decreased expression of histone deacetylase 9 (HDAC9), an enzyme responsible for removing acetyl groups from histones. A lower expression of HDAC9 might lead to hyperacetylation of histones, which can contribute to the inappropriate activation of inflammatory genes by immune cells.