DNA accessibility refers to how easily the genetic material in DNA can be accessed by proteins and other molecules that regulate gene expression. This accessibility is influenced by the structure of chromatin, which is made up of DNA wrapped around proteins called histones. When chromatin is tightly packed, DNA is less accessible, making it harder for genes to be expressed. Factors such as epigenetic modifications and transcription factors play a crucial role in determining DNA accessibility. These modifications can loosen or tighten the chromatin structure, allowing or restricting access to specific genes. This dynamic regulation is essential for proper cellular function and development.