Final answer:
The environment influences DNA expression through epigenetic changes such as DNA methylation and histone modification, which can alter gene accessibility and expression.
Step-by-step explanation:
The environment can significantly influence DNA expression through a variety of mechanisms, including epigenetic modifications such as DNA methylation and histone modification. For example, exposure to ultraviolet (UV) light can lead to epigenetic changes that affect gene expression. UV light can alter the DNA molecule directly or through influencing the modification of histones, the proteins around which DNA is wrapped. These changes can result in the DNA becoming more tightly or loosely packed, thereby altering gene accessibility for transcription and ultimately affecting how genes are expressed.
Methylation of DNA, which typically suppresses gene expression, can occur in response to environmental factors such as UV light exposure. This modification can directly impact which genes are turned on or off within a cell. Similarly, histones can undergo acetylation and deacetylation, influencing the structure of chromatin and accessibility of genes. These epigenetic changes are not permanent alterations of the DNA sequence, but rather reversible modifications that can affect gene expression and be passed on during cell division, potentially affecting multiple generations.