Final answer:
DNA packaging is influenced by the presence of methyl groups on certain cytosine nucleotides of DNA, a process known as epigenetics. Epigenetic changes can be heritable and regulate gene expression without altering the sequence of nucleotides.
Step-by-step explanation:
During DNA packaging, DNA-binding proteins called histones perform various levels of DNA wrapping and attachment to scaffolding proteins. The combination of DNA with these attached proteins is referred to as chromatin. In eukaryotes, the packaging of DNA by histones may be influenced by environmental factors that affect the presence of methyl groups on certain cytosine nucleotides of DNA. The influence of environmental factors on DNA packaging is called epigenetics. Epigenetics is another mechanism for regulating gene expression without altering the sequence of nucleotides. Epigenetic changes can be maintained through multiple rounds of cell division and, therefore, can be heritable.