Final answer:
A mutation in a histone protein gene would likely affect DNA packing, hindering the access of transcription factors and other proteins to the DNA, potentially leading to improper gene expression and associated health issues.
Step-by-step explanation:
A loss-of-function mutation in the gene coding for one of the histone proteins would likely disrupt normal nucleosome structure and function. Histones are crucial for the packing of DNA into chromatin, and they play a critical role in regulating gene expression. Without properly functioning histones, DNA could become either too tightly or too loosely packed, interfering with the necessary access for transcription factors and other DNA binding proteins.
Such a mutation could hinder the expression of various genes, possibly leading to developmental issues or diseases such as cancer. For example, histone hypo-acetylation often leads to tighter packing, which is associated with the inactivation of gene expression in the context of X chromosome inactivation in females. Conversely, histone acetylation usually correlates with looser DNA packing, allowing for gene expression.