text: Yo, listen up, I got a story to tell,
  'Bout X-linked genes and how they dwell.
  In heterozygous females, things get complex,
  Epigenetic controls, yeah, that's the context.
  
  X chromosome inactivation, that's the pathway,
  Modulating genes in a special way.
  At least four effects, let me break it down,
  In females, X-linked mental retardation's found.
  
  First, non-random X inactivation, it's wild,
  Stochastic or genetic factors, you see it's compiled.
  Tissues where one cell type takes control,
  No mosaic cell population, it's a different goal.
  
  Second, skewed inactivation, let's dive in deep,
  Normal X gets silenced, it's a secret to keep.
  Deletion of X chromosome, mentally retarded females,
  They show us how this X-linked tale unveils.
  
  Third, functional disomy, pay attention now,
  X-linked genes expressed wrong, it's a wow.
  Structurally abnormal X chromosomes, they lack the center,
  Mentally retarded females, this issue won't enter.
  
  Last but not least, dose-dependent overexpression,
  X-linked genes go wild, it's a confession.
  They "escape" X inactivation, causing delay,
  Increasing numbers of X chromosomes, that's the display.
  
  So there you have it, X-linked genes on the scene,
  In females with X-linked defects, it's a mean machine.
  Epigenetic control, shaping their fate,
  X chromosome inactivation, it's never too late.