Final answer:
True. Multiple modifications can occur simultaneously on the histone proteins, affecting nucleosome spacing and gene expression.
Step-by-step explanation:
True. Multiple modifications can occur simultaneously on the histone proteins. Histone proteins and DNA nucleotides can both undergo chemical modifications such as acetylation, de-acetylation, methylation, and phosphorylation. These modifications affect nucleosome spacing and gene expression. For example, acetylation of histones tends to unwind the nucleosomes and open the DNA for transcription, while methylation can open DNA for transcription as well. These modifications can occur simultaneously, leading to dynamic changes in chromatin structure and gene regulation.