Final answer:
The structure of histones has true epigenetic effects by chemically modifying DNA accessibility without altering the DNA sequence, affecting gene expression patterns.
Step-by-step explanation:
The statement that the structure of the histones has epigenetic effects is true. Histones are proteins around which DNA wraps to form nucleosomes, the fundamental subunits of chromatin. The chemical modifications of histones, such as acetylation and methylation, influence the packing of nucleosomes, which in turn affects the accessibility of DNA for transcription. Histone acetylation typically results in a looser packaging of nucleosomes, making the DNA more accessible for transcription and thereby affecting gene expression. This illustrates an epigenetic regulation mechanism, where modifications do not change the DNA sequence but alter gene expression patterns. These changes can be maintained through cell division, and some may even be heritable.