Final answer:
In heterochromatin formation, both sequence-specific DNA-binding proteins and non-coding RNAs are responsible for recruiting histone deacetylases and histone methyltransferases to a nucleation site, as they guide enzyme activity necessary for chromatin modification. The correct option is c.
Step-by-step explanation:
In the formation of heterochromatin, sequence-specific DNA-binding proteins and non-coding RNAs are responsible for recruiting histone deacetylases and histone methyltransferases to a nucleation site.
So the answer is (c) Both sequence-specific DNA-binding proteins and non-coding RNAs. Sequence-specific DNA-binding proteins can recognize specific sequences of DNA and initiate chromatin remodeling processes by attracting the necessary modifying enzymes.
Meanwhile, non-coding RNAs can also play a role in guiding histone modifiers to specific areas of the genome.
Essentially, changes to chromatin structure, such as acetylation, de-acetylation, methylation, and phosphorylation, are regulated by enzymes such as HAT enzymes, de-acetylases, and methyl transferases.
These reversible modifications do not change the underlying DNA sequence but affect the packing of chromatin, impacting transcription accessibility. The correct option is c.