Final answer:
Chromatin structure and accessibility of genes to RNA polymerase II and transcription machinery are important for gene expression. Chromatin can be modified to regulate gene transcription by opening up or remaining closed. Open chromatin allows RNA polymerase II and transcription factors to bind and initiate transcription, while closed chromatin prevents transcription.
Step-by-step explanation:
Chromatin structure and accessibility of genes to RNA polymerase II and transcription machinery are important for gene expression. Chromatin is composed of DNA wrapped around histone proteins, and its structure can be modified to regulate gene transcription. When a gene needs to be transcribed, the chromatin in that region can open up, allowing RNA polymerase II and transcription factors to bind to the promoter region and initiate transcription. On the other hand, if a gene needs to remain silenced, the chromatin remains in a closed configuration, preventing transcription machinery from accessing the DNA.