Final answer:
H19 lncRNA is a non-coding RNA involved in gene regulation and imprinting, where it affects the expression of genes based on parental origin.
Step-by-step explanation:
The H19 lncRNA is a long non-coding RNA that plays a crucial role in gene expression regulation and imprinting, a process where certain genes are expressed in a parent-of-origin-specific manner. Imprinting involves epigenetic marks that lead to the expression of either the maternal or paternal allele, but not both. The H19 gene, for instance, is typically maternally expressed, meaning that the copy inherited from the mother is active, while the one from the father is silenced.
During X chromosome inactivation in females, epigenetic changes occur, which affect nucleosome packaging and thus gene expression. Nucleosomes are the basic units of DNA packaging in eukaryotic cells and their organization dictates the accessibility of DNA to the transcriptional machinery. Consequently, tightly packed nucleosomes prevent gene expression, and this is what happens on the inactivated X chromosome in females. This results in dosage compensation, ensuring that males and females have similar levels of X-linked gene products.